Mammalian Cry1 and Cry2 are essential for maintenance of circadian rhythms

Many biochemical, physiological and behavioural processes show circadian rhythms which are generated by an internal time-keeping mechanism referred to as the biological clock. According to rapidly developing models, the core oscillator driving this clock is composed of an autoregulatory transcription-(post) translation-based feedback loop involving a set of 'dock' genes. Molecular clocks do not oscillate with an exact 24-hour rhythmicity but are entrained to solar day/night rhythms by light. The mammalian proteins Cryl and Cry2, which are members of the family of plant blue-light receptors (cryptochromes) and photolyases, have been proposed as candidate light receptors for photoentrainment of the biological clock. Here we show that mice lacking the Cryl or Cry2 protein display accelerated and delayed free-running periodicity of locomotor activity, respectively. Strikingly, in the absence of both proteins, an instantaneous and complete loss of free-running rhythmicity is observed. This suggests that, in addition to a possible photoreceptor and antagonistic clock-adjusting function, both proteins are essential for the maintenance of circadian rhythmicity.

ERCC6, a member of a subfamily of putative helicases, is involved in Cockayne's syndrome and preferential repair of active genes

Cells from patients with the UV-sensitive nucleotide excision repair disorder Cockayne's syndrome (CS) have a specific defect in preferential repair of lesions from the transcribed strand of active genes. This system permits quick resumption of transcription after UV exposure. Here we report the characterization of ERCC6, a gene involved in preferential repair in eukaryotes. ERCC6 corrects the repair defect of CS complementation group B (CS-B). It encodes a protein of 1493 amino acids, containing seven consecutive domains conserved between DNA and RNA helicases. The entire helicase region bears striking homology to segments in recently discovered proteins involved in transcription regulation, chromosome stability, and DNA repair. Mutation analysis of a CS-B patient indicates that the gene is not essential for cell viability and is specific for preferential repair of transcribed sequences.

Disruption of mouse RAD54 reduces ionizing radiation resistance and homologous recombination

Double-strand DNA break (DSB) repair by homologous recombination occurs through the RAD52 pathway in Saccharomyces cerevisiae. Its biological importance is underscored by the conservation of many RAD52 pathway genes, including RAD54, from fungi to humans. We have analyzed the phenotype of mouse RAD54-/- (mRAD54-/-) cells. Consistent with a DSB repair defect, these cells are sensitive to ionizing radiation, mitomycin C, and methyl methanesulfonate, but not to ultraviolet light. Gene targeting experiments demonstrate that homologous recombination in mRAD54-/- cells is reduced compared to wild-type cells. These results imply that, besides DNA end-joining mediated by DNA-dependent protein kinase, homologous recombination contributes to the repair of DSBs in mammalian cells. Furthermore, we show that mRAD54-/- mice are viable and exhibit apparently normal V(D)J and immunoglobulin class-switch recombination. Thus, mRAD54 is not required for the recombination processes that generate functional immunoglobulin and T cell receptor genes.

Disruption of mouse ERCC1 results in a novel repair syndrome with growth failure, nuclear abnormalities and senescence

BACKGROUND

The structure-specific ERCC1/XPF endonuclease complex that contains the ERCC1 and XPF subunits is implicated in the repair of two distinct types of lesions in DNA: nucleotide excision repair (NER) for ultraviolet-induced lesions and bulky chemical adducts; and recombination repair of the very genotoxic interstrand cross-links.

RESULTS

Here, we present a detailed analysis of two types of mice with mutations in ERCC1, one in which the gene is 'knocked out', and one in which the encoded protein contains a seven amino-acid carboxy-terminal truncation. In addition to the previously reported symptoms of severe runting, abnormalities of liver nuclei and greatly reduced lifespan (which appeared less severe in the truncation mutant), both types of ERCC1-mutant mouse exhibited an absence of subcutaneous fat, early onset of ferritin deposition in the spleen, kidney malfunction, gross abnormalities of ploidy and cytoplasmic invaginations in nuclei of liver and kidney, and compromised NER and cross-link repair. We also found that heterozygosity for ERCC1 mutations did not appear to provide a selective advantage for chemically induced tumorigenesis. An important clue to the cause of the very severe ERCC1-mutant phenotypes is our finding that ERCC1-mutant cells undergo premature replicative senescence, unlike cells from mice with a defect only in NER.

CONCLUSIONS

Our results strongly suggest that the accumulation in ERCC1-mutant mice of endogenously generated DNA interstrand cross-links, which are normally repaired by ERCC1-dependent recombination repair, underlies both the early onset of cell cycle arrest and polyploidy in the liver and kidney. Thus, our work provides an insight into the molecular basis of ageing and highlights the role of ERCC1 and interstrand DNA cross-links.

Inactivation of the HR6B ubiquitin-conjugating DNA repair enzyme in mice causes male sterility associated with chromatin modification

The ubiquitin-conjugating yeast enzyme RAD6 and its human homologs hHR6A and hHR6B are implicated in postreplication repair and damage-induced mutagenesis. The yeast protein is also required for sporulation and may modulate chromatin structure via histone ubiquitination. We report the phenotype of the first animal mutant in the ubiquitin pathway: inactivation of the hHR6B-homologous gene in mice causes male infertility. Derailment of spermatogenesis becomes overt during the postmeiotic condensation of chromatin in spermatids. These findings provide a parallel between yeast sporulation and mammalian spermatogenesis and strongly implicate hHR6-dependent ubiquitination in chromatin remodeling. Since heterozygous male mice and even knockout female mice are completely normal and fertile and thus able to transmit the defect, similar hHR6B mutations may cause male infertility in man.

Defective transcription-coupled repair in Cockayne syndrome B mice is associated with skin cancer predisposition

A mouse model for the nucleotide excision repair disorder Cockayne syndrome (CS) was generated by mimicking a truncation in the CSB(ERCC6) gene of a CS-B patient. CSB-deficient mice exhibit all of the CS repair characteristics: ultraviolet (UV) sensitivity, inactivation of transcription-coupled repair, unaffected global genome repair, and inability to resume RNA synthesis after UV exposure. Other CS features thought to involve the functioning of basal transcription/repair factor TFIIH, such as growth failure and neurologic dysfunction, are present in mild form. In contrast to the human syndrome, CSB-deficient mice show increased susceptibility to skin cancer. Our results demonstrate that transcription-coupled repair of UV-induced cyclobutane pyrimidine dimers contributes to the prevention of carcinogenesis in mice. Further, they suggest that the lack of cancer predisposition in CS patients is attributable to a global genome repair process that in humans is more effective than in rodents.

Molecular characterization of the human excision repair gene ERCC-1: cDNA cloning and amino acid homology with the yeast DNA repair gene RAD10

The human excision repair gene ERCC-1 was cloned after DNA mediated gene transfer to the CHO mutant 43-3B, which is sensitive to ultraviolet light and mitomycin-C. We describe the cloning and sequence analysis of the ERCC-1 cDNA and partial characterization of the gene. ERCC-1 has a size of 15 kb and is located on human chromosome 19. The ERCC-1 precursor RNA is subject to alternative splicing of an internal 72 bp coding exon. Only the cDNA of the larger 1.1 kb transcript, encoding a protein of 297 amino acids, was able to confer resistance to ultraviolet light and mitomycin-C on 43-3B cells. Significant amino acid sequence homology was found between the ERCC-1 gene product and the yeast excision repair protein RAD10. The most homologous region displayed structural homology with DNA binding domains of various polypeptides.

Molecular cloning of a human DNA repair gene

Cell strains derived from patients having a hereditary disorder associated with defects in repair of DNA damage such as xeroderma pigmentosum and mutants isolated from established rodent cell lines provide the tools for genetic and biochemical analysis of DNA repair pathways in mammalian cells. Complementation studies using these cells have illustrated the genetic and biochemical complexity of these pathways. The precise nature of the genes and gene products involved in these mutants has not yet been resolved. Isolation of repair genes by recombinant DNA technology would open up new approaches to the elucidation of repair mechanisms in mammalian cells. Here we report the molecular cloning of a human repair gene (ERCC1) that complements the repair defect in a Chinese hamster ovary (CHO) mutant cell line.

Homologous and non-homologous recombination differentially affect DNA damage repair in mice

Ionizing radiation and interstrand DNA crosslinking compounds provide important treatments against cancer due to their extreme genotoxicity for proliferating cells. Both the efficacies of such treatments and the mutagenic potential of these agents are modulated by the ability of cells to repair the inflicted DNA damage. Here we demonstrate that homologous recombination-deficient mRAD54(-/-) mice are hypersensitive to ionizing radiation at the embryonic but, unexpectedly, not at the adult stage. However, at the adult stage mRAD54 deficiency dramatically aggravates the ionizing radiation sensitivity of severe combined immune deficiency (scid) mice that are impaired in DNA double-strand break repair through DNA end-joining. In contrast, regardless of developmental stage, mRAD54(-/-) mice are hypersensitive to the interstrand DNA crosslinking compound mitomycin C. These results demonstrate that the two major DNA double-strand break repair pathways in mammals have overlapping as well as specialized roles, and that the relative contribution of these pathways towards repair of ionizing radiation-induced DNA damage changes during development of the animal.

Base excision repair deficient mice lacking the Aag alkyladenine DNA glycosylase

3-methyladenine (3MeA) DNA glycosylases remove 3MeAs from alkylated DNA to initiate the base excision repair pathway. Here we report the generation of mice deficient in the 3MeA DNA glycosylase encoded by the Aag (Mpg) gene. Alkyladenine DNA glycosylase turns out to be the major DNA glycosylase not only for the cytotoxic 3MeA DNA lesion, but also for the mutagenic 1,N6-ethenoadenine (epsilonA) and hypoxanthine lesions. Aag appears to be the only 3MeA and hypoxanthine DNA glycosylase in liver, testes, kidney, and lung, and the only epsilonA DNA glycosylase in liver, testes, and kidney; another epsilonA DNA glycosylase may be expressed in lung. Although alkyladenine DNA glycosylase has the capacity to remove 8-oxoguanine DNA lesions, it does not appear to be the major glycosylase for 8-oxoguanine repair. Fibroblasts derived from Aag -/- mice are alkylation sensitive, indicating that Aag -/- mice may be similarly sensitive.

Mouse Rad54 affects DNA conformation and DNA-damage-induced Rad51 foci formation

Error-free repair by homologous recombination of DNA double-strand breaks induced by ionizing radiation (IR) requires the Rad52 group proteins, including Rad51 and Rad54, in the yeast Saccharomyces cerevisiae [1]. The formation of a 'joint' molecule between the damaged DNA and the homologous repair template is a key step in recombination mediated by Rad51 and stimulated by Rad54 [2] [3] [4] [5]. Mammalian homologs of Rad51 and Rad54 have been identified [2] [3] [6]. Here, we demonstrate that mouse Rad54 (mRad54) formed IR-induced nuclear foci that colocalized with mRad51. Interaction between mRad51 and mRad54 was induced by genotoxic stress, but only when lesions that required mRad54 for their repair were formed. Interestingly, mRad54 was essential for the formation of IR-induced mRad51 foci. Rad54 belongs to the SWI2/SNF2 protein family, members of which modulate protein-DNA interactions in an ATP-driven manner [7]. Results of a topological assay suggested that purified human Rad54 (hRad54) protein can unwind double-stranded (ds) DNA at the expense of ATP hydrolysis. Unwinding of the homologous repair template could promote the formation or stabilization of hRad51-mediated joint molecules. Rad54 appears to be required downstream of other Rad52 group proteins, such as Rad52 and the Rad55-Rad57 heterodimer, that assist Rad51 in interacting with the broken DNA [2] [3] [4].

A mouse model for the basal transcription/DNA repair syndrome trichothiodystrophy

The sun-sensitive form of the severe neurodevelopmental, brittle hair disorder trichothiodystrophy (TTD) is caused by point mutations in the essential XPB and XPD helicase subunits of the dual functional DNA repair/basal transcription factor TFIIH. The phenotype is hypothesized to be in part derived from a nucleotide excision repair defect and in part from a subtle basal transcription deficiency accounting for the nonrepair TTD features. Using a novel gene-targeting strategy, we have mimicked the causative XPD point mutation of a TTD patient in the mouse. TTD mice reflect to a remarkable extent the human disorder, including brittle hair, developmental abnormalities, reduced life span, UV sensitivity, and skin abnormalities. The cutaneous symptoms are associated with reduced transcription of a skin-specific gene strongly supporting the concept of TTD as a human disease due to inborn defects in basal transcription and DNA repair.

The human RAD54 recombinational DNA repair protein is a double-stranded DNA-dependent ATPase

DNA double-strand break repair through the RAD52 homologous recombination pathway in the yeast Saccharomyces cerevisiae requires, among others, the RAD51, RAD52, and RAD54 genes. The biological importance of homologous recombination is underscored by the conservation of the RAD52 pathway from fungi to humans. The critical roles of the RAD52 group proteins in the early steps of recombination, the search for DNA homology and strand exchange, are now becoming apparent. Here, we report the purification of the human Rad54 protein. We showed that human Rad54 has ATPase activity that is absolutely dependent on double-stranded DNA. Unexpectedly, the ATPase activity appeared not absolutely required for the DNA repair function of human Rad54 in vivo. Despite the presence of amino acid sequence motifs that are conserved in a large family of DNA helicases, no helicase activity of human Rad54 was observed on a variety of different DNA substrates. Possible functions of human Rad54 in homologous recombination that couple the energy gained from ATP hydrolysis to translocation along DNA, rather than disruption of base pairing, are discussed.

Disruption of mouse SNM1 causes increased sensitivity to the DNA interstrand cross-linking agent mitomycin C

DNA interstrand cross-links (ICLs) represent lethal DNA damage, because they block transcription, replication, and segregation of DNA. Because of their genotoxicity, agents inducing ICLs are often used in antitumor therapy. The repair of ICLs is complex and involves proteins belonging to nucleotide excision, recombination, and translesion DNA repair pathways in Escherichia coli, Saccharomyces cerevisiae, and mammals. We cloned and analyzed mammalian homologs of the S. cerevisiae gene SNM1 (PSO2), which is specifically involved in ICL repair. Human Snm1, a nuclear protein, was ubiquitously expressed at a very low level. We generated mouse SNM1(-/-) embryonic stem cells and showed that these cells were sensitive to mitomycin C. In contrast to S. cerevisiae snm1 mutants, they were not significantly sensitive to other ICL agents, probably due to redundancy in mammalian ICL repair and the existence of other SNM1 homologs. The sensitivity to mitomycin C was complemented by transfection of the human SNM1 cDNA and by targeting of a genomic cDNA-murine SNM1 fusion construct to the disrupted locus. We also generated mice deficient for murine SNM1. They were viable and fertile and showed no major abnormalities. However, they were sensitive to mitomycin C. The ICL sensitivity of the mammalian SNM1 mutant suggests that SNM1 function and, by implication, ICL repair are at least partially conserved between S. cerevisiae and mammals.

The rate of DNA synthesis in normal human and ataxia telangiectasia cells after exposure to X-irradiation

The rate of DNA synthesis was studied in normal cell strains and in strains from patients suffering from the inherited disorder ataxia telangiectasia (AT). After exposure to relatively low doses of oxic X-rays (0-4 krad) DNA synthesis was depressed in AT cell strains to a significantly lesser extent than in normal cells. This response was observed in both an "excision-deficient" and an "excision-proficient" strain. In contrast, there was no difference in DNA-synthesis inhibition between AT and normal cells after UV exposure. After X-irradiation of cells from patients with xeroderma pigmentosum, both complementation group A and XP variants, the observed rate of DNA synthesis was equal to that in normal cells. An exception was the strain XP3BR which has been shown to be X-ray-sensitive. This strain exhibited diminished DNA synthesis inhibition after X-ray doses below 1 krad. These data suggest a relationship between hypersensitivity to X-rays and diminished depression of DNA synthesis.

Guided Internet-delivered cognitive behavioural treatment for insomnia: a randomized trial

BACKGROUND

Insomnia is a prevalent problem with a high burden of disease (e.g. reduced quality of life, reduced work capacity) and a high co-morbidity with other mental and somatic disorders. Cognitive behavioural therapy (CBT) is effective in the treatment of insomnia but is seldom offered. CBT delivered through the Internet might be a more accessible alternative. In this study we examined the effectiveness of a guided Internet-delivered CBT for adults with insomnia using a randomized controlled trial (RCT).

METHOD

A total of 118 patients, recruited from the general population, were randomized to the 6-week guided Internet intervention (n = 59) or to a wait-list control group (n = 59). Patients filled out an online questionnaire and a 7-day sleep diary before (T0) and after (T1) the 6-week period. The intervention group received a follow-up questionnaire 3 months after baseline (T2).

RESULTS

Almost three-quarters (72.9%) of the patients completed the whole intervention. Intention-to-treat (ITT) analysis showed that the treatment had statistically significant medium to large effects (p < 0.05; Cohen's d between 0.40 and 1.06), and resulted more often in clinically relevant changes, on all sleep and secondary outcomes with the exception of sleep onset latency (SOL) and number of awakenings (NA). There was a non-significant difference in the reduction in sleep medication between the intervention (a decrease of 6.8%) and control (an increase of 1.8%) groups (p = 0.20). Data on longer-term effects were inconclusive.

CONCLUSIONS

This study adds to the growing body of literature that indicates that guided CBT for insomnia can be delivered through the Internet. Patients accept the format and their sleep improves.

Characteristics of long-term asymptomatic infection with human immunodeficiency virus type 1 in men with normal and low CD4+ cell counts

From a cohort study of homosexual men in Amsterdam, 61 human immunodeficiency virus (HIV)-infected men who had remained asymptomatic for at least 7 years were identified. In a nested case control study, these men were compared with 142 men who progressed symptomatic HIV infection (CDC class IV) within 7 years, regarding laboratory markers, sexual behavior, psychologic coping, and drug use. Of the 61 long-term asymptomatic men, 13 had a CD4+ cell count > or = 500/mm3 after 7 years; in 2 of these 13, the CD4+ cell count had not declined during follow-up. Independent of CD4+ cell count, long-term asymptomatic HIV-1 infection was characterized by stable T cell reactivity after stimulation with monoclonal CD3 antibodies, seropositivity for antibodies to HIV core proteins, and the absence of hepatitis B markers. No association with markers of high-risk sex or the recreational use of drugs was found. Long-term asymptomatic men had a slightly lower score regarding the coping behavior active problem-solving; no other associations with coping behaviors were found.

Increase in the share of steady partners as a source of HIV infection: a 17-year study of seroconversion among gay men

OBJECTIVES

To examine the share of steady versus casual partners as the source of HIV infection in gay male seroconversions between 1984 and 2000 and the effect of age at seroconversion on the source of HIV transmission.

METHODS

The sample consisted of 144 seroconverstors from the Amsterdam Cohort Study among Homosexual Men. Questionnaires and post-seroconversion interviews were used to determine the source of HIV transmission.

RESULTS

Analysis revealed an interaction effect between calendar year and age at seroconversion (P < 0.05). Younger seroconverters had higher odds ratios [odds ratio, 11.33; 95% confidence interval, 1.77--72.13] to be infected by their steady partner late in the AIDS epidemic: 15% (three of 20) between 1984 and 1987 versus 67% (six of nine) between 1994 and 2000. No such time effect was present for older seroconverters who were consistently more likely to be infected by a casual partner: 79% (37 of 47) between 1984 and 1987, and 83% (15 of 18) between 1994 and 2000.

CONCLUSIONS

Young gay seroconverters today are more likely to have contracted HIV from a steady partner than from a casual partner, compared with early in the AIDS epidemic and compared also with older gay seroconverters. There is a pressing need for preventive measures addressing sexual risk behaviour within steady relationships among younger gay men.

Expression of the ubiquitin-conjugating DNA repair enzymes HHR6A and B suggests a role in spermatogenesis and chromatin modification

RAD6, a member of the expanding family of ubiquitin-conjugating (E2) enzymes, functions in the so-called "N-rule" protein breakdown pathway of Saccharomyces cerevisiae. In vitro, the protein can attach one or multiple ubiquitin (Ub) moieties to histones H2A and B and trigger their E3-dependent degradation. Rad6 mutants display a remarkably pleiotropic phenotype, implicating the protein in DNA damage-induced mutagenesis, postreplication repair, repression of retrotransposition, and sporulation. RAD6 transcription is strongly induced upon UV exposure and in meiosis, suggesting that it is part of a damage-induced response pathway and that it is involved in meiotic recombination. It is postulated that the protein exerts its functions by modulating chromatin structure. Previously, we have cloned two human homologs of this gene (designated HHR6A and HHR6B) and demonstrated that they partially complement the yeast defect. Here we present a detailed characterisation of their expression at the transcript and protein levels. Both HHR6 proteins, resolved by 2-dimensional immunoblot analysis, are expressed in all mammalian tissues and cell types examined, indicating that both genes are functional and constitutively expressed. Although the proteins are highly conserved, the UV induction present in yeast is not preserved, pointing to important differences in damage response between yeast and mammals. Absence of alterations in HHR6 transcripts or protein upon heat shock and during the cell cycle suggests that the proteins are not involved in stress response or cell cycle regulation. Elevated levels of HHR6 transcripts and proteins were found in testis. Enhanced HHR6 expression did not coincide with meiotic recombination but with the replacement of histones by transition proteins. Immunohistochemistry demonstrated that the HHR6 proteins are located in the nucleus, consistent with a functional link with chromatin. Electron microscopy combined with immunogold labeling revealed a preferential localisation of HHR6 in euchromatin areas, suggesting that the protein is associated with transcriptionally active regions. Our findings support the idea that both HHR6 genes have overlapping, constitutive functions related to chromatin conformation and that they have a specific role in spermatogenesis, involving Ub-mediated histone degradation.

Prospective assessment of the influence of pancreatic cancer resection on exocrine pancreatic function

Background

Exocrine insufficiency frequently develops in patients with pancreatic cancer owing to tumour ingrowth and pancreatic duct obstruction. Surgery might restore this function by removing the primary disease and restoring duct patency, but it may also have the opposite effect, as a result of resection of functional parenchyma and anatomical changes. This study evaluated the course of pancreatic function, before and after pancreatic resection.

Methods

This prospective cohort study included patients with tumours in the pancreatic region requiring pancreatic resection in a tertiary referral centre between March 2010 and August 2012. Starting before surgery, exocrine function was determined monthly by measuring faecal elastase 1 levels (normal value over 0·200 µg per g faeces). Endocrine function, steatorrhoea-related symptoms and bodyweight were also evaluated before and after surgery. Subjects were followed from diagnosis until 6 months after surgery, or until death.

Results

Twenty-nine patients were included, 12 with pancreatic cancer, 14 with ampullary carcinoma and three with bile duct carcinoma (median tumour size 2·6 cm). Twenty-six patients underwent pancreaticoduodenectomy and three distal pancreatectomy. Thirteen patients had exocrine insufficiency at preoperative diagnosis. After a median follow-up of 6 months, this had increased to 24 patients. Diabetes was present in seven patients at diagnosis, and developed in one additional patient within 1 month after surgery.

Conclusion

Most patients with tumours in the pancreatic region requiring pancreatic resection either had exocrine insufficiency at diagnosis or became exocrine-insufficient soon after surgical resection.

Hypersensitivity to ionizing radiation, in vitro, in a new chromosomal breakage disorder, the Nijmegen Breakage Syndrome

The Nijmegen Breakage Syndrome (NBS) is a new chromosomal instability disorder different from ataxia telangiectasia (AT) and other chromosome-breakage syndromes. Cells from an NBS patient appeared hypersensitive to X-irradiation. X-rays induced significantly more chromosomal damage in NBS lymphocytes and fibroblasts than in normal cells. The difference was most pronounced after irradiation in G2. Further, NBS fibroblasts were more readily killed by X-rays than normal fibroblasts. In addition, the DNA synthesis in NBS cells was more resistant to X-rays and bleomycin than that in normal cells. The reaction of NBS cells to X-rays and bleomycin was similar to that of cells from patients with ataxia telangiectasia. Our results indicate that NBS and AT, which also have similar chromosomal characteristics, must be closely related.

miR-10b-5p is a novel Th17 regulator present in Th17 cells from ankylosing spondylitis

OBJECTIVE

To determine the microRNA (miR) signature in ankylosing spondylitis (AS) T helper (Th)17 cells.

METHODS

Interleukin (IL)-17A-producing CD4+ T cells from patients with AS and healthy controls were FACS-sorted for miR sequencing and qPCR validation. miR-10b function was determined by miR mimic expression followed by cytokine measurement, transcriptome analysis, qPCR and luciferase assays.

RESULTS

AS Th17 cells exhibited a miR signature characterised by upregulation of miR-155-5p, miR-210-3p and miR-10b. miR-10b has not been described previously in Th17 cells and was selected for further characterisation. miR-10b is transiently induced in in vitro differentiated Th17 cells. Transcriptome, qPCR and luciferase assays suggest that MAP3K7 is targeted by miR-10b. Both miR-10b overexpression and MAP3K7 silencing inhibited production of IL-17A by both total CD4 and differentiating Th17 cells.

CONCLUSIONS

AS Th17 cells have a specific miR signature and upregulate miR-10b in vitro. Our data suggest that miR-10b is upregulated by proinflammatory cytokines and may act as a feedback loop to suppress IL-17A by targeting MAP3K7. miR-10b is a potential therapeutic candidate to suppress pathogenic Th17 cell function in patients with AS.

Gay men who are not getting tested for HIV

Using data from Australian Gay Community Periodic Surveys 1998-2010, we assessed the prevalence, trends and characteristics of gay men not tested for HIV. In 2010, one in eight Australian gay socially-engaged men were never tested for HIV, most of them sexually active and 56.5 % reporting unprotected anal intercourse. The proportion of not tested men was significantly higher in men younger than 30, of non-European origin and living outside of gay metropolitan areas. Although frequency of testing was associated with sexual practices, significant proportions of men with multiple sex partners and reporting unprotected anal intercourse were not tested as recommended. There were issues with using gay-friendly testing services in gay metropolitan areas. Despite Australia's success in HIV testing, improvement is needed for early detection of HIV infections. Interventions should encourage regular testing, engage with young gay men, improve access and convenience of testing, train service providers and expand testing options.

Molecular cloning and biological characterization of the human excision repair gene ERCC-3

In this report we present the cloning, partial characterization, and preliminary studies of the biological activity of a human gene, designated ERCC-3, involved in early steps of the nucleotide excision repair pathway. The gene was cloned after genomic DNA transfection of human (HeLa) chromosomal DNA together with dominant marker pSV3gptH to the UV-sensitive, incision-defective Chinese hamster ovary (CHO) mutant 27-1. This mutant belongs to complementation group 3 of repair-deficient rodent mutants. After selection of UV-resistant primary and secondary 27-1 transformants, human sequences associated with the induced UV resistance were rescued in cosmids from the DNA of a secondary transformant by using a linked dominant marker copy and human repetitive DNA as probes. From coinheritance analysis of the ERCC-3 region in independent transformants, we deduce that the gene has a size of 35 to 45 kilobases, of which one essential segment has so far been refractory to cloning. Conserved unique human sequences hybridizing to a 3.0-kilobase mRNA were used to isolate apparently full-length cDNA clones. Upon transfection to 27-1 cells, the ERCC-3 cDNA, inserted in a mammalian expression vector, induced specific and (virtually) complete correction of the UV sensitivity and unscheduled DNA synthesis of mutants of complementation group 3 with very high efficiency. Mutant 27-1 is, unlike other mutants of complementation group 3, also very sensitive toward small alkylating agents. This unique property of the mutant is not corrected by introduction of the ERCC-3 cDNA, indicating that it may be caused by an independent second mutation in another repair function. By hybridization to DNA of a human x rodent hybrid cell panel, the ERCC-3 gene was assigned to chromosome 2, in agreement with data based on cell fusion (L. H. Thompson, A. V. Carrano, K. Sato, E. P. Salazar, B. F. White, S. A. Stewart, J. L. Minkler, and M. J. Siciliano, Somat. Cell. Mol. Genet. 13:539-551, 1987).