The Effect of Individual or Study-Wide Report-Back on Knowledge, Concern, and Exposure-Reducing Behaviors Related to Endocrine-Disrupting Chemicals

BACKGROUND

To make informed decisions about endocrine-disrupting chemicals (EDCs), people need functional understanding of exposures and health and an ability to act on their knowledge. The return of biomonitoring results is an opportunity to educate people about EDCs and motivate exposure reduction.

OBJECTIVES

This study investigates environmental health knowledge about EDCs, concerns about health effects, and exposure-reducing behaviors before and after the return of individual-level exposure results or only study-wide results.

METHODS

Women in the Child Health and Development Studies who were biomonitored for 42 EDCs were randomly assigned to receive a report with personal chemical results or only study-wide findings. We interviewed participants before and after report-back about their knowledge and concerns about EDCs and how frequently they performed exposure-related behaviors. We investigated baseline differences by education and race and examined changes after report-back by race and report type.

RESULTS

Participants (n = 135 ) demonstrated general understanding of exposure pathways and health impacts of EDCs. For 9 out of 20 knowledge questions, more than 90% of participants (n ≥ 124 ) gave correct responses at baseline, including for questions about chemicals' persistence in the body and effects of early-life exposure. Most participants held two misconceptions-about chemical safety testing in the United States and what doctors can infer from EDC results-although errors decreased after report-back. Initially, concern was higher for legacy pollutants, but report-back increased concern for consumer product chemicals. After report-back, participants took some actions to reduce exposures, particularly to per- and polyfluoroalkyl substances, and total behavior was associated with knowledge and concern but not race, education, or report type.

DISCUSSION

This study demonstrated that participants had foundational knowledge about EDCs and that report-back further built their environmental health literacy. We conclude that future communications should target misconceptions about chemicals regulation in the United States, because information about regulations is crucial for people to evaluate risks posed by consumer product chemicals and decide whether to engage with public policy. https://doi.org/10.1289/EHP12565.

Outcomes from Returning Individual versus Only Study-Wide Biomonitoring Results in an Environmental Exposure Study Using the Digital Exposure Report-Back Interface (DERBI)

BACKGROUND

Study participants want to receive their biomonitoring results for environmental chemicals, and ethics guidelines encourage reporting back. However, few studies have quantitively assessed participants' responses to individual exposure reports, and digital methods have not been evaluated.

OBJECTIVES

We isolated effects of receiving personal results vs. only study-wide findings and investigated whether effects differed for Black participants.

METHODS

We randomly assigned a subset of 295 women from the Child Health and Development Studies, half of whom were Black, to receive a report with personal environmental chemical results or only study-wide (aggregate) findings. Reports included results for 42 chemicals and lipids and were prepared using the Digital Exposure Report-Back Interface (DERBI). Women were interviewed before and after viewing their report. We analyzed differences in website activity, emotional responses, and intentions to participate in future research by report type and race using Wilcoxon rank sum tests, Wilcoxon-Pratt signed ranks tests, and multiple regression.

RESULTS

The personal report group spent approximately twice as much time on their reports as the aggregate group before the post-report-back interview. Among personal-report participants (n=93), 84% (78) viewed chemical group information for at least one personal result highlighted on their home page; among aggregate-report participants (n=94), 66% (62) viewed any chemical group page. Both groups reported strong positive feelings (curious, informed, interested, respected) about receiving results before and after report-back and mild negative feelings (helpless, scared, worried). Although most participants remained unworried after report-back, worry increased by a small amount in both groups. Among Black participants, higher post report-back worry was associated with having high levels of chemicals.

CONCLUSIONS

Participants were motivated by their personal results to access online information about chemical sources and potential health effects. Report-back was associated with a small increase in worry, which could motivate appropriate action. Personal report-back increased engagement with exposure reports among Black participants. https://doi.org/10.1289/EHP9072.

Development and Evaluation of a Training Program for Community-Based Participatory Research in Breast Cancer

This paper describes the development and feasibility of the Community Based Research Infrastructure to Better Science (CRIBS) training. The goal of this training program was to help new or existing community-academic teams to build strong partnerships and successfully develop together fundable research projects focused on breast cancer environmental causes and disparities. A comprehensive mixed-methods participatory approach was utilized to assess the training. Twenty-two community-academic teams applied for the training program; twelve teams were enrolled. All teams completed the training and subsequently submitted research applications for funding. All components of the training received high ratings and positive qualitative comments. Self-rated competency in all of the learning domains increased during the training. Four (33%) of teams were successful in their first attempt to garner research funding, and six (50%) were eventually successful. The evaluation of CRIBS found it to have successfully achieved all four goals of the training: (1) Twelve new CBPR (community-based participatory research) teams, (2) improved knowledge about CBPR and science, (3) twelve submitted grant proposals in the first year, and (4) six (50%) successfully funded research projects.

California Breast Cancer Prevention Initiatives: Setting a research agenda for prevention

The environment is an underutilized pathway to breast cancer prevention. Current research approaches and funding streams related to breast cancer and the environment are unequal to the task at hand. We undertook the California Breast Cancer Prevention Initiatives, a four-year comprehensive effort to set a research agenda related to breast cancer, the environment, disparities and prevention. We identified 20 topics for Concept Proposals reflecting a life-course approach and the complex etiology of breast cancer; considering the environment as chemical, physical and socially constructed exposures that are experienced concurrently: at home, in the community and at work; and addressing how we should be modifying the world around us to promote a less carcinogenic environment. Redirecting breast cancer research toward prevention-oriented discovery could significantly reduce the incidence and associated disparities of the disease among future generations.

Abstract B05: Technical assistance as part of capacity building for collaborative research in breast cancer, the environment, and/or disparities

Training and technical assistance efforts for community based participatory research (CBPR) partnerships have the potential to improve outcomes in both scientific rigor and collaboration. Successful competition for regional or national funding for CBPR represents a critical step in this trajectory. To this end, a collaboration funded through this NIEHS award has developed and implemented an intensive training program (Community Based Research Infrastructure to Better Science [CRIBS]) to build capacity among community-academic teams to conduct CBPR into disparities in breast cancer and/or environmental causes of breast cancer. The program includes face-to-face training; online training; mock grant review; and technical assistance (TA); and skill-building in creating CBPR partnerships; understanding the science of the environmental causes of and disparities in breast cancer; creating a pathway from vision to project; and writing successful grant applications. Participants in the training included 31 individuals in 12 partnerships with at least one community and one academic member in each. Fifty-five percent of participants identified as belonging to an ethnic or racial minority group; 81% identified as female; 58% identified as community partners; the mean age was 49.76 years old (median = 52; range = 23 to 71). Partnerships came from twelve locations across California. TA efforts began in the second month of F2F trainings and included: a) four, monthly, tailored, in-person consultations of up to 1.5 hrs in length; b) review of an 8-page concept paper prepared by each team; c) four, monthly, tailored one-hour phone consultations. TA was provided by CRIBS staff and representatives from national funding organizations with expertise in scientific and collaborative aspects of breast cancer research, as well as by experts in the field of CBPR, disparities, and the environment. Over time, improved clarity and specificity were evident in the research questions formulated across partnerships. Implications of tailored, technical assistance for partnerships embarking on CBPR in disparities are discussed.

Citation Format: Senaida Fernandez, Marj Plumb, Catherine Thomsen, Braun Susan, Heather Sarantis, Juliana van Olphen, Emily Galpern, Marion Kavanaugh-Lynch. Technical assistance as part of capacity building for collaborative research in breast cancer, the environment, and/or disparities. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr B05.

Assessing process and outcomes: evaluating community-based participatory research

BACKGROUND

The California Breast Cancer Research Program (CBCRP) Community Research Collaboration (CRC) Awards fund research projects conducted by partnerships between community members and academically trained research scientists.

OBJECTIVES

We sought to determine the relationship, if any, between the collaborative process of conducting the CRC projects and reported outcomes.

METHODS

Community and academic researchers from the first seven CRC full award projects were interviewed in one-on-one, standardized, semistructured telephone interviews. Twelve of thirteen eligible community partners and all nine eligible academic partners were interviewed (some teams had multiple community or academic partners). Interview questions covered four major types of outcomes (improved methodology [four items], benefited community [sixitems], benefited researchers [three items], or influenced health services and policy [five items]) and three major aspects of the partnership (collaboration among partners [three items], group dynamics [five items], and community involvement [two items]). Process and outcome scores for each team were compared using a scatter plot graph.

RESULT

Teams were most effective at improving the quality of research methodology, providing benefits to the participating community agency, and answering questions important to the communities involved. Areas of difficulty for the teams included collaborative data analysis, power sharing, and managing the impact of turnover. Although the projects varied in the measures of the partnership process, the three teams that had the highest outcome scores also had the highest scores for the partnership process.

CONCLUSIONS

Although the relationship between process and outcomes is not necessarily causal, these results suggest an association worthy of further investigation.

Target cell frequency is a genetically determined risk factor in radiation leukaemogenesis

Whole body exposure to ionizing radiation increases the risk of radiation-induced acute myeloid leukaemia (r-AML). r-AML is the result of the accumulation of mutations in a single haemopoietic stem cell, so risk is therefore a function of the number of mutations required to transform the stem cell and the mutation rate. There is a genetic component to the risk of AML within the general population, and low penetrance variant alleles encoding DNA repair enzymes have been genetically implicated in therapy-related AML susceptibility. However, what is largely ignored is that target cell number, which defines the number of genomes at risk from DNA damaging agents, is also part of the equation that defines risk. We will review the evidence from genetic studies of inbred mouse models that target cell frequency is a risk factor in radiation leukaemogenesis. Inbred mouse strains that differ in their susceptibility to radiation-induced r-AML and thymic lymphoma (r-TL), spontaneous TL and pristane-induced plasmacytoma (PCT) have been exploited to identify susceptibility loci. The target cell in AML is the haemopoietic stem cell, whereas TLs and PCT arise from more mature lymphoid progenitor cells. Inbred mice also differ significantly in all aspects of haemopoiesis, and these differences have been used to identify quantitative trait loci (QTL) that determine the frequency of specific haemopoietic stem, progenitor or mature blood cells. The co-localization of QTL that determine risk and target cell frequency in all three haemopoietic malignancies is strong evidence that target cell frequency is a risk factor in radiation leukaemogenesis.

The late radiotherapy normal tissue injury phenotypes of telangiectasia, fibrosis and atrophy in breast cancer patients have distinct genotype-dependent causes

The relationship between late normal tissue radiation injury phenotypes in 167 breast cancer patients treated with radiotherapy and: (i) radiotherapy dose (boost); (ii) an early acute radiation reaction and (iii) genetic background was examined. Patients were genotyped at single nucleotide polymorphisms (SNPs) in eight candidate genes. An early acute reaction to radiation and/or the inheritance of the transforming growth factor-β1 (TGFβ1 −509T) SNP contributed to the risk of fibrosis. In contrast, an additional 15 Gy electron boost and/or the inheritance of X-ray repair cross-complementing 1 (XRCC1) (R399Q) SNP contributed to the risk of telangiectasia. Although fibrosis, telangiectasia and atrophy, all contribute to late radiation injury, the data suggest that they have distinct underlying genetic and radiobiological causes. Fibrosis risk is associated with an inflammatory response (an acute reaction and/or TGFβ1), whereas telangiectasia is associated with vascular endothelial cell damage (boost and/or XRCC1). Atrophy is associated with an acute response, but the genetic predisposing factors that determine the risk of an acute response or atrophy have yet to be identified. A combined analysis of two UK breast cancer patient studies shows that 8% of patients are homozygous (TT) for the TGFβ1 (C-509T) variant allele and have a 15-fold increased risk of fibrosis following radiotherapy (95% confidence interval: 3.76–60.3; P=0.000003) compared with (CC) homozygotes.

Mouse bone marrow and peripheral blood erythroid cell counts are regulated by different autosomal genetic loci

Erythropoiesis is under fine control and genetic loci that affect it are likely to be important in a range of conditions. To assess the relative contributions of different genetic loci to parameters of erythropoiesis, we have measured RBC counts in the peripheral circulation and committed erythroid cells (RBC and small normoblasts) in the bone marrow in a cohort of (CBA/H x C57BL/6) F2 mice to map quantitative trait loci (QTL). Candidate genes were assessed using bioinformatics and DNA sequencing. Different autosomal loci affect bone marrow (chromosomes 5, 11 and 19) and peripheral blood (chromosome 4) erythroid cell counts but there may be a common chromosome X locus. Spleen weight QTL were found on chromosomes 3, 15 and 17. Surprisingly, erythropoietin (Epo) is the best candidate quantitative trait gene (QTG) in the chromosome 5 locus that affects bone marrow but not peripheral blood erythroid cell counts. Epo gene expression is known to be genetically regulated in mice, but our data suggest a tissue-specific role for epo in mouse erythropoiesis that is also genetically determined. The identity of the other QTG will be important both to further knowledge of the control of erythropoiesis and as potential modifier genes for haematological disorders.

Funding community-based participatory research: lessons learned

The California Breast Cancer Research Program (CBCRP) was created to fund innovative breast cancer research specifically addressing the needs of women in California. Beginning in 1997, the Program launched the Community Research Collaboration (CRC) Program, a Community-Based Participatory Research (CBPR) program intended to foster community-researcher collaboration on all aspects of the research process, essentially placing the community in the center of the research paradigm. The CBCRP conducted a process evaluation of the CRC Program to assess success and identify areas for improvement. The evaluation included community-researcher collaborations and the award process. The evaluation identified successes that speak to the effectiveness of the collaboration concept: empowering women to formulate and initiate research; involving underserved and hard-to-reach populations; addressing important and useful research questions; increasing communities' skills and expertise, and enabling lasting collaborations. The greatest weakness identified was the involvement of the broader community (beyond the group/organization involved) in these projects. The evaluation identified strengths in CBCRP's award process, including technical assistance and feedback, the emphasis on collaboration in the review process, and awarding funds directly to community groups. Barriers included: power imbalances due to the community's lack of experience in the dominant research funding culture; funding limits and award delays; and the increased service demand beyond the funding limits of the award that is created. The CBCRP has been able to incorporate many of the evaluation findings to improve the CRC Program.

Evidence of genetic instability in 3 Gy X-ray-induced mouse leukaemias and 3 Gy X-irradiated haemopoietic stem cells

PURPOSE

If radiation-induced genetic instability is causal in mouse radiation leukaemogenesis, then genetic instability should be detectable in the irradiated target untransformed haemopoietic stem cell, and evidence of genetic instability detected in the clonal radiation-induced leukaemia. We have tested this hypothesis using the CBA/H mouse model of radiation-induced acute myeloid leukaemia (r-AML).

MATERIALS AND METHODS

Fluorescence in situ hybridisation (FISH) was employed to screen for chromosomal aberrations in mouse 3 Gy X-ray-induced r-AMLs and in the clonal descendents of control and 3 Gy X-irradiated bone marrow haemopoietic stem cells using the in vitro clonogenic CFU-A colony assay.

RESULTS

High levels of clonal non-specific chromosomal aberrations were detected in the r-AML (approximately 4-5 aberrations/r-AML), and ongoing chromosomal instability as defined by subclonal variants detected in 5/10 r-AML. A similar analysis of CFU-A colonies revealed chromosomal aberrations in 25% of colonies derived from irradiated bone marrow (2% in controls). However, 66% of the aberrant colonies (2% in controls) exhibited ongoing genetic instability as defined by non-clonal chromosomal aberrations. Overall, 6% (121/1884) of the CFU-A cells derived from irradiated bone marrow were aberrant (0.05% in controls) of which 12% (15/121) were subclonal. No one CFU-A cell exhibited aberrations on more than one of the three chromosomes painted.

CONCLUSIONS

The high levels of non-specific genetic damage observed in the r-AMLs is therefore attributed to the accumulation of genetic lesions in the target haemopoietic stem cell over a longer time-scale after exposure than assessed in the in vitro CFU-A clonogenic assay. This is consistent with the long latency of the multi-stage radiation leukaemogenic process, and a role for radiation-induced genetic instability is inferred.

Allelic loss on chromosome 4 (Lyr2/TLSR5) is associated with myeloid, B-lympho-myeloid, and lymphoid (B and T) mouse radiation-induced leukemias

The CBA/H mouse model of radiation-induced acute myeloid leukemia (AML) was re-examined using molecular approaches. In addition to the typical promyelocytic AMLs, 34% were reclassified as early pre-B lympho-myeloid leukemias (L-ML) based on leukemic blood cell morphology, immunoglobulin heavy-chain gene re-arrangements (IgH(R)), or expression of both lymphoid (Vpre-B1 and Rag1) and myeloid (myeloperoxidase and lysozyme M) genes. Allelic loss on chromosome 4 was frequently detected in AMLs (53%) and L-MLs (more than 95%), and the preferential loss of the maternally transmitted allele suggests the locus may be imprinted. A minimally deleted region (MDR) maps to a 3.4-cM interval, which is frequently deleted in radiation-induced thymic lymphomas (TLSR5) and contains a recessive, maternally transmitted genetic locus (Lyr2) that confers resistance to spontaneous and radiation-induced pre-B and T cell lymphomas, suggesting they are one and the same. Thus, the Lyr2/TLSR5 locus is frequently implicated in myeloid, lymphoid (B and T), and mixed-lineage mouse leukemias and lymphomas. Epigenetic inactivation of one Lyr2/TLSR5 allele during normal mouse development suggests that only a single hit is required for its inactivation during leukemogenesis, and this may be a significant contributing factor to the efficiency of the leukemogenic process in the mouse.

Undercounts and overstatements: will the IOM report on lesbian health improve research?

In January 1999, the Institute of Medicine (IOM) released a report on lesbian health research that fulfills 3 goals: it provides an extensive review of much of the research that has been done on the health of women who have sex with other women, it addresses the methodological and ethical issues inherent in conducting research on this population, and it suggests avenues for further research. This report will likely help lesbian health researchers gain funding, publish further research in medical journals, and receive support and validation from medical and research institutions. To ensure that such research is useful, benefits the lesbian community, and expands the understanding of lesbian health conditions, particular attention needs to be paid to the methods and definitions used and to the involvement of the lesbian community in designing, implementing, and analyzing the research itself.

Susceptibility to radiation-induced leukaemia/lymphoma is genetically separable from sensitivity to radiation-induced genomic instability

PURPOSE

To determine whether there is a relationship between the genetics underlying the susceptibility to radiation-induced leukaemia in CBA/H (acute myeloid leukaemia, AML) and C57BL/6 (thymic lymphoma, TL) mice, and the genetics underlying the sensitivity of CBA/H (sensitive) and C57BL/6 (resistant) mice to radiation-induced chromosomal instability.

MATERIALS AND METHODS

CBA/H, (CBA/H x C57BL/6)F1, F1 x CBA/H, F1 x C57BL/6 and F1 x F1 mice were exposed to a single acute dose of 3.0 Gy X-rays. AML and TL were diagnosed over the subsequent 30 months.

RESULTS

There was no statistically significant difference in the incidence of AML in F1, F1 x F1, F1 x CBA/H and F1 x C57BL/6 mice, which was approximately 50% that in CBA/H mice. AML susceptibility is therefore a dominant polygenic trait, and both susceptibility and resistance (variable penetrance) CBA/H and C57BL/6 loci are involved. The incidence of TL in the FM and F1 x CBA/H mice was negligible, indicating that TL susceptibility is a recessive trait. As the TL incidence in the F1 x C57BL/6 mice was about half that in C57BL/6 mice, one recessive locus is probably involved.

CONCLUSIONS

AML susceptibility in CBA/H mice is a dominant trait in contrast to the recessive inheritance of CBA/H sensitivity to radiation-induced chromosomal instability. TL-susceptibility in C57BL/6 is a recessive trait in contrast to the dominant inheritance of C57BL/6 resistance to radiation-induced chromosomal instability.

No correlation between germline mutation at repeat DNA and meiotic crossover in male mice exposed to X-rays or cisplatin

To test the hypothesis that mouse germline expanded simple tandem repeat (ESTR) mutations are associated with recombination events during spermatogenesis, crossover frequencies were compared with germline mutation rates at ESTR loci in male mice acutely exposed to 1Gy of X-rays or to 10mg/kg of the anticancer drug cisplatin. Ionising radiation resulted in a highly significant 2.7-3.6-fold increase in ESTR mutation rate in males mated 4, 5 and 6 weeks after exposure, but not 3 weeks after exposure. In contrast, irradiation had no effect on meiotic crossover frequencies assayed on six chromosomes using 25 polymorphic microsatellite loci spaced at approximately 20cM intervals and covering 421cM of the mouse genome. Paternal exposure to cisplatin did not affect either ESTR mutation rates or crossover frequencies, despite a report that cisplatin can increase crossover frequency in mice. Correlation analysis did not reveal any associations between the paternal ESTR mutation rate and crossover frequency in unexposed males and in those exposed to X-rays or cisplatin. This study does not, therefore, support the hypothesis that mutation induction at mouse ESTR loci results from a general genome-wide increase in meiotic recombination rate.

Induction of minisatellite mutations in the mouse germline by low-dose chronic exposure to gamma-radiation and fission neutrons

Germline mutation induction at mouse minisatellite loci by paternal low-dose (0.125-1 Gy) exposure to chronic (1.66 x 10(-4) Gy min(-1)) low-linear energy transfer (low-LET) gamma-irradiation and high-LET fission neutrons (0.003 Gy min(-1)) was studied at pre-meiotic stages of spermatogenesis. Both types of radiation produced linear dose-response curves for mutation of the paternal allele. In contrast to previous results using higher doses, the pattern of induction of minisatellite mutation after chronic gamma-irradiation was similar to acute (0.5 Gy min(-1)) exposure to X-rays, indicating that the elevated mutation rate was independent of the ability of the cell to repair damage induced immediately or over a period of up to 100 h. Chronic exposure to fission neutrons was more effective than acute or chronic low-LET exposure (relative biological effectiveness, RBE=3.36). The data also provide strong support for the previous conclusion that increases in minisatellite mutation rate are not caused by radiation-induced DNA damage at minisatellite loci themselves, but rather from damage induced by ionising radiation elsewhere in the genome/cell.

Allelic loss and promoter hypermethylation of the p15INK4b gene features in mouse radiation-induced lymphoid - but not myeloid - leukaemias

Mouse radiation-induced acute myeloid leukaemias (AMLs) which arose in a (CBA/H x C57BL/6) genetic background have a 45% incidence of loss of heterozygosity (LOH) on chromosome 4. Frequent chromosome 4 LOH in mouse radiation-induced (C57BL/6 x RF/J) thymic lymphomas (TLs) is associated with promoter/exon 1 region hypermethylation of the remaining p15INK4b and p16INK4a alleles, so this may be common to mouse radiation myeloid and lymphoid leukaemogenesis. We addressed the question of p15INK4b/p16INK4a/p19ARF gene promoter hypermethylation in radiation-induced AMLs by comparison to TLs which arose in a similar (C57BL/6 x CBA/H) genetic background as a consequence of the same initiating dose of 3 Gy X-rays. Only one homozygous deletion was detected in the approximately 100 leukaemias analysed. p15INK4b gene promoter/exon 1 hypermethylation was readily detected (21%) in the lymphoid but not myeloid (3.1%) leukaemias, and p16INK4a and p19ARF gene promoter/exon 1 methylation was rare (<3%) in both. Thus, allelic loss and promoter hypermethylation of the p15INK4b gene is particular to radiation-induced lymphoid leukaemias and is independent of p16INK4a and p19ARF gene promoter/exon 1 hypermethylation.

Specificity of loss of heterozygosity in radiation-induced mouse myeloid and lymphoid leukaemias

PURPOSE

To determine whether loss of heterozygosity (LOH) at specific chromosomal loci in radiation-induced leukaemias, arising in a similar genetic background, is leukaemia-type specific (myeloid versus lymphoid) or common to both.

MATERIALS AND METHODS

Leukaemias that arose in 3 Gy X-irradiated (CBA/H x C57BL/6)F1 intercross and backcross mice were diagnosed as acute myeloid leukaemia (AML) or thymic lymphoma (TL). LOH was determined using 28 polymorphic microsatellite markers distributed over seven chromosomes using control and leukaemic DNA from individual mice.

RESULTS

LOH incidences of 0-20% were observed at most loci in both leukaemia types. Specific LOH incidences of 38-76% were observed for myeloid (chromosome 2) and lymphoid (chromosomes 11 and 14) leukaemias. Chromosome 4 LOH was frequently (38-50%) observed in both types, although the commonly deleted regions differed. LOH was detected at either chromosome 2 or 4 in AML and either chromosome 4 or 11 in TL.

CONCLUSIONS

LOH incidences of 38-76% suggest a causal role of particular loci which is mainly, but not exclusively, dependent on leukaemia type. LOH incidences of 0-20% at other loci in both leukaemias suggest that many genetic deletions are non-causal and incidental in radiation-leukaemogenesis.

An E mu-BCL-2 transgene facilitates leukaemogenesis by ionizing radiation

Clonogenic murine B cell precursors are normally ultrasensitive to apoptosis following genotoxic exposure in vitro but can be protected by expression of an E mu-BCL-2 transgene. Such exposures are likely to be mutagenic. This in turn suggests that a level of in vivo genotoxic exposure that usually has minimal pathological consequences might become leukaemogenic when damaged cells fail to abort by apoptosis. If this were to be the case, then the cell type that becomes leukaemic and the chromosomal/molecular changes that occur would also be of considerable interest. We tested this possibility by exposing E mu-BCL-2 and wild-type mice of differing ages to a single dose of X-irradiation of 1-4 Gy. Young (approximately 4-6 weeks) transgenic mice developed leukaemia at a high rate following exposure to 2 Gy but adult mice (4-6 months) did not. Exposure to 4 Gy produced leukaemia in both young and adult transgenic mice but at a higher frequency in the former. Leukaemic cell populations showed clonal rearrangements of the IGH gene but in most cases analysed had immunophenotypic features of an early B lympho-myeloid progenitor population which has not previously been recorded in radiation leukaemogenesis. Molecular cytogenetic analysis of leukaemic cells by banded karyotype and FISH revealed a consistent double abnormality: trisomy 15 plus an interstitial deletion of chromosome 4 that was confirmed by LOH analysis.

Radiation-induced germline instability at minisatellite loci

PURPOSE

To review the results of recent studies on radiation-induced germline instability at mammalian minisatellite loci.

RESULTS

Evidence has been obtained recently that germline mutation at minisatellites is remarkably sensitive to ionizing radiation, in both mice and humans. In mice, an elevated mutation rate was found after acute irradiation of pre-meiotic spermatogonia, with a doubling dose of 0.33 Gy, a value close to those obtained in mice after acute spermatogonia irradiation using other systems for mutation detection. In humans, analysis of germline mutation rate at minisatellites among children born in areas of the Mogilev district of Belarus, which was heavily polluted after the Chernobyl accident, has shown a twofold higher mutation rate in exposed families compared with non-irradiated families from the United Kingdom. Within the Belarus cohort, the mutation rate was significantly greater in families exposed to a higher parental radiation dose, consistent with radiation induction of germline mutation. The data in this study also demonstrate the indirect nature of radiation-induced germline mutation at mammalian minisatellite loci suggesting a strong similarity with the phenomenon of genomic instability in somatic cells.

CONCLUSIONS

Minisatellite loci provide a powerful system for the efficient monitoring of germline mutation in humans and are capable of detecting induced mutations in relatively small population samples.

Genetic instability in radiation-induced leukaemias: mouse models

PURPOSE

Genetic instability plays a major role in multi-stage carcinogenesis. Ionizing radiation induces delayed genetic instability which can be transmitted to the clonal offspring of the irradiated cell, so it is of considerable importance to determine whether radiation-induced genetic instability contributes to radiation-leukaemogenesis.

RESULTS

The experimental data obtained using radiation-induced leukaemias in mouse models were reviewed, and an attempt was made to distinguish between the instability detectable in de novo cancers and that which is associated with ionising radiation. Genetic lesions identified in mouse leukaemias include non-clonal chromosomal aberrations, loss of heterozygosity, and minisatellite/microsatellite mutations.

CONCLUSIONS

Studies of mouse radiation-induced leukaemias have detected evidence of genetic instability. However, with few exceptions, most of this instability was also observed during de novo multi-stage carcinogenesis. This raises the possibility that radiation induces ongoing genetic instability that is functionally indistinguishable to that implicated in de novo tumour progression.

Stage specificity, dose response, and doubling dose for mouse minisatellite germ-line mutation induced by acute radiation

Germ-line mutation induction at mouse minisatellite loci by acute irradiation with x-rays was studied at premeiotic and postmeiotic stages of spermatogenesis. An elevated paternal mutation rate was found after irradiation of premeiotic spermatogonia and stem cells, whereas the frequency of minisatellite mutation after postmeiotic irradiation of spermatids was similar to that in control litters. In contrast, paternal irradiation did not affect the maternal mutation rate. A linear dose-response curve for paternal mutation induced at premeiotic stages was found, with a doubling dose of 0.33 Gy, a value close to those obtained in mice after acute spermatogonia irradiation using other systems for mutation detection. High frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be evaluated at low doses of exposure in very small population samples, which currently makes minisatellite DNA the most powerful tool for monitoring radiation-induced germ-line mutation.

Ongoing Y-chromosome instability defines sub-clonal variants in radiation-induced leukaemias in the mouse

Forty primary leukaemias that arose in vivo as a consequence of 3 Gy X-irradiation of inbred mouse strains were analysed for Y-chromosome aberrations by conventional cytogenetics and fluorescent in situ hybridization (FISH). Compared with control mice which were X-irradiated but which exhibited no overt signs of leukaemia, the loss and gain of Y-chromosomes in leukaemic spleen cells defined subclonal variants in the radiation-induced haemopoietic malignancies that arose in CBA/H, DBA/2 and (C57BL/6 x DBA/2)F1 mice. This Y-chromosome instability was significantly higher than that observed in spleen cells of age-matched (or older) irradiated control mice that had not developed overt leukaemia. The detection of Y-chromosome aberrations is considered in the context of the high numbers of potential gene regulatory sequences in the murine Y-chromosome and the potential for the insertional activation of cellular genes during multi-stage radiation leukaemogenesis.

Mini- and microsatellite mutations in radiation-induced acute myeloid leukaemia in the CBA/H mouse

Radiation-induced acute myeloid leukaemia (AML) in the CBA/H mouse is a clonal disorder and therefore amenable to the analysis of genetic instability during radiation leukaemogenesis. The genotype of a single minisatellite and 20 microsatellite loci was compared in tail and leukaemic spleen DNA prepared from the same mouse. Somatic mutation at the Ms6-hm minisatellite locus was nearly seven times higher (27%, 4/15) than the spontaneous germline mutation rate (4%). Only 1/15 AMLs exhibited microsatellite mutations, but 5/20 loci were mutated in the same AML, indicating that it was deficient in mismatch repair. Thus, whereas somatic minisatellite mutations, which are associated with complex intra-allelic gene conversion events, occur at a very high rate in the radiation-induced AMLs, microsatellite instability, which has been associated with the acquisition of the replication error repair (RER+) phenotype, is infrequent but detectable.

A polymorphic and hypervariable locus in the pseudoautosomal region of the CBA/H mouse sex chromosomes

We have identified a genomic locus (DXYH1) that is polymorphic and hypervariable within the CBA/H colony. Using a panel of C57BL/6 x Mus spretus backcross offspring, it was mapped to the distal end of the X chromosome. Pseudoautosomal inheritance was demonstrated through three generations of CBA/H x CBA/H and CBA/H x C57BL/6 crosses and confirmed through linkage to the Sxr locus in X/Y Sxr x 3H1 crosses. Meiotic recombination frequencies place DXYH1 similar 28% into the pseudoautosomal region from the boundary. The de novo generation of CBA/H variant DXYH1 restriction fragment length polymorphisms during spermatogenesis is suggestive of the germline instability associated with hypermutable human minisatellites. The absence of DXYH1-related sequences in Mus spretus provides DNA sequence evidence to support the observed failure of X-Y pairing during meiosis and consequent hybrid infertility in C57BL/6 x Mus spretus male F1 offspring.

Co-amplification to tail-to-tail copies of MuRVY and IAPE retroviral genomes on the Mus musculus Y chromosome

We have isolated a clone from a C57BL/6 genomic library that contains both part of the Y Chromosome-specific 8.7 kbp MuRVY genome (Hutchinson and Eicher, J. Virol. 63, 4043, 1989) and a full-length 8.3 kbp Intracisternal A Particle genome (IAPE-Y), in a tail-to-tail organization. Although IAPs are encoded by a disperse multigene family (approximately 1000 copies per haploid genome), we present evidence that a significant proportion of the IAP-related sequences are present on the Y Chromosome (Chr) and that a >25 kbp genomic sequence, which contains the two proviral genomes, has been amplified on the Y Chr. Two discrete amplified families of MuRVY retroviral genomes distinguishable by a polymorphic restriction site were detected, suggestive that amplification occurred in incremental stages. The presence of MuRVY-related DNA sequences, but absence of IAPE-Y-related DNA sequences in Mus spretus suggests that the IAPE-Y retrotransposition event occurred after the evolutionary divergence of the lineages leading to Mus musculus and Mus spretus, and that the amplification of MuRVY occurred independently in the two lineages.

Regulatory elements in the first intron of the mouse Ha-ras gene

The Ha-ras gene is one of the three oncogenes (Ha-ras, Ki-ras, and N-ras) of the ras superfamily of small G proteins. The p21ras proteins encoded by the ras genes are key proteins involved in the transduction of signals from membrane receptor-tyrosine kinases to downstream targets. The ras genes seem to play a ubiquitous role in the control of cell proliferation and cell differentiation. At the same time, ras genes may perform specific differentiated functions in certain cell types. Little is known about the regulation of expression of the Ha-ras gene. The first intron of the Ha-ras gene has been reported to be highly conserved between human and rodent. We investigated the role that this intron may play in the regulation of expression of Ha-ras. The promoter region of the Ha-ras gene exhibits characteristics of a housekeeping gene. Deletion analysis shows the existence of an enhancer-type element in the 5' region of the first intron (intron 0). DNase 1 footprinting experiments reveal five sites that interact with nuclear proteins from fibroblast and epithelial cell lines. Deletion and site-directed mutagenesis of three of these sites show that two are involved in a positive effect and one in a negative effect on the regulation of expression of the mouse Ha-ras gene.

Complex Y chromosome aberrations are a recurrent secondary event in radiation-induced murine acute myeloid leukaemia

Arbitrarily primed-PCR analysis of DNA from male CBA/H radiation-induced leukaemic spleens revealed the loss of an approximately 350-bp sequence in several leukaemias. We have isolated a lambda EMBL3 C57BL/6 genomic subclone (pJB1) which hybridizes to the AP-PCR probe and is located on the Y chromosome. Southern blot analyses using the pJB1 probe indicate that the genomic sequence was deleted in five of 14 leukaemias. Cytogenetic analyses of 31 X-ray induced leukaemias in male CBA/H mice revealed, in addition to the characteristic partial deletion of chromosome 2 (28/31 leukaemias), a high incidence (16/31) of the loss of an intact Y chromosome. Comparison of the Southern blot and cytogenetic analyses of the leukaemias demonstrate a significant lack of correspondence between the loss of an intact Y chromosome and Y chromosome-specific DNA sequences, suggesting that Y chromosome aberrations are complex. Whereas partial deletion of chromosome 2 can be detected in 6% of bone marrow cells within 6-11 days of irradiation, no Y chromosome involvement was detected, indicating that Y chromosome aberrations are a late event in radiation-induced leukaemogenesis. These findings are comparable to the loss of sex chromosomes in human t(8;21) AML.

An ATF/CREB-binding site is essential for cell-specific and inducible transcription of the murine MIP-1 beta cytokine gene

The murine macrophage inflammatory protein 1 beta mRNA (MIP-1 beta) is rapidly and transiently induced in macrophages by lipopolysaccharide (LPS), serum or cycloheximide. Functional studies of the MIP-1 beta proximal promoter indicate that it is cell-specific, and serum- and LPS-responsive in macrophages. A 76-bp proximal promoter sequence (-51 to -127 bp) confers cell-specific and LPS-inducible activity when placed upstream from a heterologous promoter in both orientations. One essential cis-regulatory element within the enhancer-like sequence is an activating transcription factor/cAMP response element (CRE)-binding protein (ATF/CREB)-binding site, although the promoter is not cAMP responsive. Electrophoretic mobility shift assays and mutational analyses suggest that the promoter site is bound by nuclear protein complexes containing cAMP-independent members of the ATF/CREB family of proteins and c-Jun, and are functionally distinct from the AP1-related TPA-response element (TRE) binding activity.

C/EBP, NF-kappa B, and c-Ets family members and transcriptional regulation of the cell-specific and inducible macrophage inflammatory protein 1 alpha immediate-early gene

Macrophage inflammatory protein 1 alpha (MIP-1 alpha) cytokine gene expression is restricted to a limited number of cells of hemopoietic origin and is rapidly and transiently induced by serum and endotoxin in macrophages. A single nuclear DNase I-hypersensitive site, which maps to the proximal promoter of the MIP-1 alpha gene, was identified in macrophage cells but was absent in cells which do not express basal levels of MIP-1 alpha mRNA. The proximal promoter sequences (+36 to -220 bp) are sufficient to confer cell-specific and inducible transcription in transfection assays. In vitro DNA-binding studies revealed five major nuclear protein binding sites in the proximal promoter which bind C/EBP, NF-kappa B, and/or c-Ets family members. Cell-specific differences in DNA binding by members of the NF-kappa B and c-Ets families correlate with the cell-specificity of MIP-1 alpha gene expression and the chromosomal conformation of the promoter. Changes in promoter binding by members of the C/EBP and NF-kappa B families correlate with the transcriptional up-regulation observed in serum- or endotoxin-stimulated macrophages in functional studies.

Hemopoietic stem cell inhibitor (SCI/MIP-1 alpha) also inhibits clonogenic epidermal keratinocyte proliferation

The maintenance and regulation of continuously renewing tissues is ultimately controlled at the level of stem-cell proliferation. We have recently identified a reversible inhibitor of hemopoietic stem-cell proliferation (stem-cell inhibitor [SCI]), which is identical to the macrophage inflammatory protein, MIP-1 alpha, a 69-amino-acid heparin-binding cytokine. To test the cell/tissue specificity of the inhibition of proliferation by SCI/MIP-1 alpha, we have investigated its activity on epidermal keratinocytes, the principal cell type of another continuously renewing tissue. Here we show that SCI/MIP-1 alpha inhibits the proliferation of epidermal keratinocytes in vitro and that the MIP-1 alpha mRNA is present in epidermal Langerhans cells but not in keratinocytes. This suggests an important growth regulatory function for SCI/MIP-1 alpha in keratopoiesis, as well as hemopoiesis, and may also indicate a novel role for the epidermal Langerhans cell. As SCI/MIP-1 alpha can inhibit the proliferation of embryologically distinct precursor cells, this raises the possibility that it may also function in a number of other tissues.

Expression of stem cell inhibitor (SCI) gene in patients with bone marrow failure

Stem cell inhibitor (SCI) has been shown to inhibit the proliferation of primitive progenitors. The inhibitor, a product of bone marrow macrophages, activated lymphocytes, and monocytes, is identical to macrophage inflammatory protein (MIP-1 alpha). We report homologous (SCI/hMIP-1 alpha) sequences in freshly isolated lymphocytes, monocytes, and granulocytes and have found that SCI mRNA can be induced in monocytes by lipopolysaccharide (LPS) and interleukins 1, 2, and 6. In contrast, interferon gamma (IFN-gamma) decreases the expression of SCI/hMIP-1 alpha. Although only a low level expression of SCI/hMIP-1 alpha mRNA can be detected in normal human bone marrow nucleated cells (NCBM), very significant increases in the levels of SCI/hMIP-1 alpha RNA transcripts are observed in NCBM from patients with aplastic anemia (AA) and myelodysplastic syndrome (MDS). These data suggest that the expression of SCI/hMIP-1 alpha in bone marrow may reflect dysregulated cytokine production and activation of the immune system that may possibly contribute to disease progression.

Hypopituitarism stabilizes the renal and retinal complications of diabetes mellitus

In 1953, Poulsen described the remarkable case of a woman with type I diabetes mellitus who experienced resolution of her retinopathy following postpartum pituitary necrosis. Since that time, many investigators have pursued the hypothesis that anterior pituitary hormones, particularly growth hormone, play a role in the pathogenesis of the microvascular complications of diabetes mellitus. While most observers have demonstrated the importance of growth hormone in the initiation and progression of diabetic retinopathy, the role of growth hormone in the development of diabetic nephropathy has been more difficult to document. In this case report, we describe a woman with long-standing type I diabetes mellitus complicated by retinopathy and nephropathy whose complications stabilized as she developed growth hormone deficiency.

Derepression of mouse beta-major-globin gene transcription during erythroid differentiation

Functional analysis of the mouse beta-major-globin gene promoter has revealed a negative regulatory element (-100 to -250 bp) which represses promoter activity in mouse erythroleukemia (MEL) cells. Promoter activity is induced 14-fold during terminal differentiation of MEL cells. Three major in vitro binding sites for NF1 (-250 bp), GATA-1 (-212 bp), and a sequence at -165 bp (BB1) have been defined in this region. Site-directed mutagenesis of any one of the three sites resulted in a five- to sixfold up-regulation of promoter activity in uninduced MEL cells, but only three- to fourfold stimulation was observed from the mutant promoters during MEL cell terminal differentiation. This finding suggests that all three sites are required for repressor activity in uninduced MEL cells and that derepression occurs during MEL cell differentiation. BB1 DNA-binding activity decreases during MEL cell differentiation, suggesting a central role for this factor in modulating the effects of the repressor element. The BB1-binding factor also competes with the CCAAT-binding protein for binding the CCAAT motif. The fact that a reduced but significant stimulation of promoter activity during differentiation is observed in the absence of the repressor element raises the possibility that the BB1 factor also down-regulates transcription in undifferentiated MEL cells by displacing binding of CCAAT-binding protein to the proximal CCAAT motif.

Characterization of hypersensitive sites, protein-binding motifs, and regulatory elements in both promoters of the mouse porphobilinogen deaminase gene

Porphobilinogen deaminase, the third enzyme in the heme biosynthetic pathway, is encoded by a gene having two different promoters. Differential splicing of transcripts from the promoters yields two distinct mRNA species that are translated to give two isoforms of the protein. One isoform is ubiquitous, whereas the other is erythroid-specific. In this study, we have analyzed the gene regulatory elements that contribute to the tissue-specific promoter utilization of the mouse porphobilinogen deaminase gene. Six nuclear DNase I-hypersensitive sites were mapped in erythroid and nonerythroid cells, and four of these regions were further analyzed for in vitro nuclear protein-binding sites. The erythroid-specific promoter contains three erythroid nuclear factor GF-1-binding sites. The proximal GF-1-binding site, together with an adjacent duplicated CACCC motif, was sufficient to confer erythroid-specific expression in functional studies. Furthermore, as upstream gene sequences were shown to greatly increase promoter activity in erythroid cells, it suggests an upstream erythroid-specific enhancer may also be required for the up-regulation of the erythroid-specific promoter during erythropoiesis.

Nuclear factor 1 activates the feline leukemia virus long terminal repeat but is posttranscriptionally down-regulated in leukemia cell lines

A recombinant feline leukemia virus (FeLV) proviral clone (T17T-22) with a long terminal repeat (LTR) which differs from prototype FeLV by a point mutation within a conserved nuclear factor 1 (NF1)-binding motif in the LTR enhancer domain was found to be poorly expressed after DNA transfection. The NF1 point mutation reduced in vitro protein binding as assessed by gel shift analysis and reduced promoter activity significantly (2- to 10-fold). However, the degree of promoter impairment due to the NF1 site mutation varied according to cell type and was least severe in a feline leukemia cell line (T3) which had low levels of nuclear NF1 DNA-binding activity. Low NF1 DNA-binding activity was observed in three FeLV-induced leukemia cell lines (T3, T17, and FL74) and in murine F9 embryonal carcinoma cells. While similar levels of NF1 gene mRNA transcripts were detected in all cell lines, Western immunoblot analysis of F9, T17, and FL74 but not T3 nuclear extracts revealed very low levels of nuclear NF1 protein. These results indicate that NF1 activity is down-regulated in FeLV-induced leukemia cells by diverse posttranscriptional mechanisms. We suggest that NF1 down-regulation may be an important characteristic of target cells susceptible to FeLV transformation in vivo and may provide the selective pressure which favors duplication of the LTR core enhancer sequence in T-cell leukemogenic FeLV variants.

Structural analysis of the mouse c-Ha-ras gene promoter

Previous studies have demonstrated that the mouse c-Harvey ras proto-oncogene (c-Ha-ras) promoter sequences are GC rich and contain several potential transcription factor SP1 binding sites. We investigated the endonuclease hypersensitivity of this region in nuclei in vitro and whole mouse tissues in vivo and identified a very strong, ubiquitous hypersensitive site covering the proximal promoter sequences. Footprint protection studies using nuclear extracts from various cell types including fibroblasts, erythroid cells, and both normal and transformed epithelial cells revealed a consistent protein-binding pattern. Five protein binding sites were observed, four of which correlated with potential SP1 binding sites. Competition experiments using an oligonucleotide corresponding to a consensus SP1 binding site confirmed that these sequences were indeed bound by the SP1 (or SP1-like) trans-acting factor. In addition, no differences were observed between the footprint patterns obtained using extracts from cells of different lineages or between normal and transformed epithelial cells carrying activated ras genes. The controlling elements responsible for differential c-Ha-ras transcription between cell types or at different stages of carcinogenesis therefore probably lie in other regions of the gene.

Synergy between the NF-E1 erythroid-specific transcription factor and the CACCC factor in the erythroid-specific promoter of the human porphobilinogen deaminase gene

A 114-base-pair promoter fragment of the human porphobilinogen deaminase gene functioned in an erythroid-specific manner in transient transfection experiments. Site-directed mutagenesis of the binding site for the erythroid-specific transcription factor (NF-E1) or an adjacent CACCC motif abolished the promoter activity. Increasing the spacing between these sites progressively reduced promoter activity, but there was no evidence that a critical alignment of the two factors on the DNA helix was required.

Structural diversity and nuclear protein binding sites in the long terminal repeats of feline leukemia virus

The long terminal repeat U3 sequences were determined for multiple feline leukemia virus proviruses isolated from naturally occurring T-cell tumors. Heterogeneity was evident, even among proviruses cloned from individual tumors. Proviruses with one, two, or three repeats of the long terminal repeat enhancer sequences coexisted in one tumor, while two proviruses with distinct direct repeats were found in another. The enhancer repeats are characteristic of retrovirus variants with accelerated leukemogenic potential and occur between -155 and -244 base pairs relative to the RNA cap site. The termini of the repeats occur at or near sequence features which have been recognized at other retrovirus recombinational junctions. In vitro footprint analysis of the feline leukemia virus enhancer revealed three major nuclear protein binding sites, located at consensus sequences for the simian virus 40 core enhancer, the nuclear factor 1 binding site, and an indirect repeat which is homologous to the PEA2 binding site in the polyomavirus enhancer. Only the simian virus 40 core enhancer sequence is present in all of the enhancer repeats. Cell type differences in binding activities to the three motifs may underlie the selective process which leads to outgrowth of viruses with specific sequence duplications.

GATAAG; a cis-control region binding an erythroid-specific nuclear factor with a role in globin and non-globin gene expression

An erythroid-specific nuclear protein factor binds to a sequence motif (GATAAG) which is present in the promoter region of the mouse alpha and beta major globin genes, and in the erythroid-specific promoter of the human porphobilinogen deaminase (PBG-D) gene. The protein activity is conserved across species, being found in mouse erythroleukaemia (MEL) cells, chicken erythrocytes, the human erythroid K562 and KMOE cell lines, but not in a variety of non-erythroid mouse tissues or in HeLa cells. Functional analysis of this element in the alpha globin gene promoter by stable transfection experiments show that the GATAAG motif resides in a 68 bp sequence which has a stimulatory effect on transcription in mouse erythroleukaemia but not fibroblast cells. The GATAAG motif is conserved in the promoters and 3' enhancers of a variety of globin and non-globin genes implying that it is a cis-element involved in the tissue-specific up-regulation of several genes that are co-expressed during erythroid cell differentiation.

Regulation of erythroid cell-specific gene expression during erythropoiesis

The aim of our group's work over the past few years has been to investigate the molecular mechanisms regulating erythroid cell-specific gene expression during erythroid cell differentiation. In addition to the alpha-globin gene, we have focussed on two non-globin genes of interest encoding the rabbit red cell-specific lipoxygenase (LOX) and the mouse glutathione peroxidase (GSHPX), an important seleno-enzyme responsible for protection against peroxide-damage. Characterisation of the GSHPX gene showed that the seleno-cysteine residue in the active site of the enzyme is encoded by UGA, which usually functions as a translation-termination codon. This novel finding has important implications regarding mRNA sequence context effects affecting codon recognition. The regulation of the GSHPX and red cell LOX genes has been investigated by functional transfection experiments. The 700 bp upstream of the GSHPX promoter seems to function equally well when linked to the bacterial chloramphenicol acetyl transferase (CAT) gene and transfected into mouse erythroid or fibroblast cell lines. However, the presence of tissue-specific DNase I hypersensitive sites (DHSS) in the 3' flanking region of the GSHPX gene suggests that such sites may be important in its regulation in the various cell types in which it is highly expressed, i.e., erythroid cells, liver and kidney. The transcription unit of the RBC LOX gene has also been defined and 5' and 3' flanking regions are being investigated for erythroid-specific regulatory elements: a region upstream of the LOX gene gives increased expression of a linked CAT gene when transfected into mouse erythroid cell lines compared to non-erythroid cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)

cis and trans control of erythroid cell-specific gene expression during erythropoiesis

The overall aim of our group's work is to investigate the molecular mechanisms regulating erythroid cell-specific gene expression during erythroid cell differentiation. We have been successful in cloning two non-globin genes of interest: the first encodes the rabbit red cell-specific lipoxygenase (LOX), which has a role in degrading mitochondrial lipids during maturation of the reticulocyte to the erythrocyte; and the second, mouse glutathione peroxidase (GSHPX), an important seleno-enzyme responsible for protection against peroxide-damage. Characterization of the GSHPX gene revealed that the seleno-cysteine residue in the active site of the enzyme is encoded by UGA, which usually functions as a translation-termination codon. This novel finding has important implications regarding the role of mRNA sequence context effects in codon recognition. In contrast with the beta-globin locus, very little is known about the mechanisms responsible for the erythroid-specific expression of the alpha-globin genes. By a combination of functional transfection assays and studies of the interactions of nuclear sequence-specific DNA-binding proteins with promoter sequences in vitro, we have recently defined two regions upstream of the mouse alpha-globin gene involved in its erythroid-specific expression: one contains a sequence motif (GATAAG) that binds to a species-conserved and erythroid-specific factor both in vitro and in vivo. Interestingly, GATAAG motifs binding the same factor are found also in the mouse and chicken adult beta-globin gene promoters, the erythroid-specific promoter of the haem pathway enzyme, porphobilinogen (PBG) deaminase and the chicken beta-globin 3' enhancer. We are now commencing purification of this erythroid-specific GATAAG-binding factor, investigating in more detail how it functions in relation to other globin gene control regions and determining whether GATAAG-like regions have a functional role in the erythroid-specific expression of other genes. We have begun to investigate the regulation of the GSHPX and red cell LOX genes. The presence of tissue-specific 3' DNAse I-hypersensitive sites (DHSS) suggests that different 3' flanking regions of the GSHPX gene may be important in its regulation in the various cell types in which it is highly expressed, i.e. erythroid cells, liver and kidney.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of neighbouring bases on G-specific DNA cleavage mediated by treatment with the anti-diol epoxide of benzo[a]pyrene in vitro

Three 5'-end-labelled double-stranded linear DNA fragments of defined sequence were treated with r-7, t-8-dihydroxy-t-9, 10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE). The DNA samples were then examined by gel electrophoresis both before and after denaturation and treatment with alkali. The extent of modification of deoxyguanosine (dG) residues was estimated from changes in electrophoretic mobility: at saturation less than 25% of the dG residues appeared to be modified by reaction with anti-BPDE. The determination of the sites of G-specific strand cleavage in a total of 0.5 kbp of DNA by sequencing gel electrophoresis showed that scission at dG residues is sequence specific and that whilst, for example, cleavage occurred at the central dG residues of all 5'-CGG-3' (21/21), of all 5'-TGG-3' (14/14), of all 5'-TGT-3' (7/7) and of all 5'-CGT-3' (5/5) sequences examined, it did not occur in any of the 5'-GGA-3' (0/12) or 5'-GGC-3' (0/15) sequences and only occurred rarely in the 5'-GGG-3' (1/48) and 5'-GGT-3' (2/11) sequences. No cleavage was found at internal dG residues within poly(dG)9 or poly(dG)18 sequences. The data may permit prediction of the sites of strand scission in DNA molecules of known sequence that have been modified by diol-epoxides of polycyclic hydrocarbons.