Development of computational models for the purpose of conducting individual livestock and premises traceback investigations utilizing National Animal Identification System-compliant data

Many of the efforts surrounding the development of the National Animal Identification System have encompassed the identification of livestock production and handling premises as well as individuals or herds of animals, whereas little effort has been directed toward the ultimate goal of animal traceback within 48 h. A mock data set representative of the Colorado cattle population was created for modeling of cattle traceability. Using this data set, algorithms were developed to complete rapid and accurate traceback and traceforward of animals or premises or both. On July 19, 2005, the Colorado Department of Public Health and Environment, in conjunction with the Colorado Department of Agriculture, conducted a test exercise pertaining to homeland security. The exercise team randomly identified animal number 926,583 (of the 2 million total animals) as a potentially infected animal of interest and requested a traceback of this animal. Traceback was accomplished in 215 s, and 540 primary coresident animals were identified. However, due to animal movements, the number of coresidents (animals exposed, directly or indirectly, to the animal of interest) expanded with coresidency level (level 1 = direct contact; level 2 = direct contact with an animal that had direct contact with the animal of interest; level 3 = direct contact with an animal that had contact with an animal that had direct contact with the animal of interest, etc.) to more than 1.2 million coresidents at level 4, and more than 90% of all animals identified as a coresident at some level. In addition to the coresidency results, the premises containing the coresidents were identified and sorted by the number of coresidents. Because of animal movement, all 19,391 premises included in the data set had coresidents at some level. This exercise demonstrated the capability of the developed algorithms to complete rapid traceback and the complexity of the resulting animal traceback output.

Diffuse basal ganglia or thalamus hyperechogenicity in preterm infants

OBJECTIVE

To determine the incidence and factors associated with diffuse basal ganglia or thalamus hyperechogenicity (BGTH) in preterm infants.

STUDY DESIGN

(1) Review of serial neurosonograms among neonates with gestational age (GA) <34 weeks born at Weiler Hospital during a 21-month period; (2) Color Doppler flow imaging; (3) Case-control study using GA group-matched controls; and (4) Blind reading of CT scans or MRIs in patients with BGTH.

RESULTS

Among 289 infants, 24 (8.3%) had diffuse BGTH. Color Doppler flow imaging was normal in nine patients. The incidence of diffuse BGTH was inversely related to GA (P<0.01). Logistic regression (n=96) showed that diffuse BGTH was significantly associated with requirement of high-frequency oscillation (HFO) (P=0.031), severe intraventricular hemorrhage (IVH) (P=0.004), hypotension requiring vasopressors (P=0.040), hypoglycemia (P=0.031) and male gender (P=0.014). Most patients with diffuse BGTH had normal basal ganglia and thalamus on CT/MRI, one had a hemorrhage, and one had an ischemic infarction.

CONCLUSIONS

In our series, diffuse BGTH occurred in 8.3%, and was associated with factors similar to those previously reported. In contrast, several series have reported almost exclusively linear or punctuate hyperechoic foci, corresponding to hyperechogenicity of the lenticulostriate vessels. Our data provide further evidence to suggest that diffuse BGTH and hyperechogenicity of the lenticulostriate vessels are two different entities. Additional studies are required to determine the long-term significance of diffuse BGTH.

Melanoma therapy via peptide-targeted {alpha}-radiation

PURPOSE

The therapeutic efficacy of a unique melanoma-targeting peptide conjugated with an in vivo generated alpha-particle-emitting radionuclide was evaluated in the B16/F1 mouse melanoma animal model. alpha-Radiation is densely ionizing, resulting in high concentrations of destructive radicals and irreparable DNA double-strand breaks. This high linear energy transfer overcomes radiation-resistant tumor cells and oxygen effects resulting in potentially high therapeutic indices in tumors such as melanoma.

EXPERIMENTAL DESIGN

The melanoma targeting peptide, 1,4,7,10-tetraazacyclodecane-1,4,7,10-tetraacetic acid (DOTA)-Re(Arg(11))CCMSH, was radiolabeled with (212)Pb, the parent of (212)Bi, which decays via alpha and beta decay. Biodistribution and therapy studies were done in the B16/F1 melanoma-bearing C57 mouse flank tumor model.

RESULTS

(212)Pb[DOTA]-Re(Arg(11))CCMSH exhibited rapid tumor uptake and extended retention coupled with rapid whole body disappearance. Radiation dose delivered to the tumor was estimated to be 61 cGy/muCi (212)Pb administered. Treatment of melanoma-bearing mice with 50, 100, and 200 muCi of (212)Pb[DOTA]-Re(Arg(11))CCMSH extended their mean survival to 22, 28, and 49.8 days, respectively, compared with the 14.6-day mean survival of the placebo control group. Forty-five percent of the mice receiving 200 muCi doses survived the study disease-free.

CONCLUSIONS

Treatment of B16/F1 murine melanoma-bearing mice with (212)Pb[DOTA]-Re(Arg(11))CCMSH significantly decreased tumor growth rates resulting in extended mean survival times, and in many cases, complete remission of disease. (212)Pb-DOTA-Re(Arg(11))CCMSH seems to be a very promising radiopharmaceutical for targeted radionuclide therapy of melanoma.

Evaluation of beta-absorbed fractions in a mouse model for 90Y, 188Re, 166Ho, 149Pm, 64Cu, and 177Lu radionuclides

Several short-lived, high-energy beta emitters are being proposed as the radionuclide components for molecular- targeted potential cancer therapeutic agents. The laboratory mice used to determine the efficacy of these new agents have organs that are relatively small compared to the ranges of these high-energy particles. The dosimetry model developed by Hui et al. was extended to provide realistic beta-dose estimates for organs in mice that received therapeutic radiopharmaceuticals containing (90)Y, (188)Re, (166)Ho, (149)Pm, (64)Cu, and (177)Lu. Major organs in this model included the liver, spleen, kidneys, lungs, heart, stomach, small and large bowel, thyroid, pancreas, bone, marrow, carcass, and a 0.025-g tumor. The study as reported in this paper verifies their results for (90)Y and extends them by using their organ geometry factors combined with newly calculated organ self-absorbed fractions from PEREGRINE and MCNP. PEREGRINE and MCNP agree to within 8% for the worst-case organ with average differences (averaged over all organs) decreasing from 5% for (90)Y to 1% for (177)Lu. When used with typical biodistribution data, the three different models predict doses that are in agreement to within 5% for the worst-case organ. The beta-absorbed fractions and cross-organ-deposited energy provided in this paper can be used by researchers to predict mouse-organ doses and should contribute to an improved understanding of the relationship between dose and radiation toxicity in mouse models where use of these isotopes is favorable.

Hormonal regulation of hepatic organic anion transporting polypeptides

Organic anion transporting polypeptides (Oatp) mediate the transport of a wide variety of amphipathic organic substrates. Rat Oatp1b2 and human OATP1B3 are members of a liver-specific subfamily of Oatps/OATPs. We investigated whether prolactin (PRL) and growth hormone (GH) regulated Oatp1b2 and OATP1B3 gene expression via signal transducers and activators of transcription 5 (Stat5). Binding sites for Stat5 transcription factors were located in the promoters of Oatp1b2 and OATP1B3 at -209 to -201 (5'-TTCTGGGAA-3') and -170 to -162 (5'-TTCTGAGAA-3'), respectively. In primary hepatocytes from female and male rats treated with PRL or GH, Oatp1b2 mRNA measured by real-time polymerase chain reaction was significantly induced 2-fold. HepG2 cells were transiently transfected with expression vectors containing Oatp1b2 or OATP1B3 promoter fragments, cDNAs for Stat5a, and the receptors for PRL (PRLR(L)) or GH (GHR), and treated with PRL or GH. PRL and GH induction of Oatp1b2 and OATP1B3 promoter activity required cotransfection of Stat5a and PRLR(L) or GHR. Mutation of the Stat5 binding site in both promoters eliminated hormonal induction. In DNA binding assays, HepG2 cells transfected with cDNAs for Stat5a and PRLR(L) were treated with PRL, and nuclear extracts were probed with a (32)P-labeled oligomer corresponding to -177 to -157 of the OATP1B3 promoter. PRL enhanced the binding of Stat5a to the OATP1B3 promoter and DNA-protein binding was inhibited in competition assays by excess OATP1B3 and Stat5 consensus oligomers but not by mutant Stat5 oligomers. These findings indicate that PRL and GH can regulate Oatp1b2 and OATP1B3 gene expression via the Stat5 signal-transduction pathway.

Pm-149 DOTA bombesin analogs for potential radiotherapy. in vivo comparison with Sm-153 and Lu-177 labeled DO3A-amide-betaAla-BBN(7-14)NH(2)

Promethium-149 (149Pm) is one of only three radiolanthanides that can be prepared in no carrier added concentrations. This high specific activity radiolanthanide is thus suitable for targeting limited numbers of specific receptors found on many tumor cells. Promethium-149 is a moderate energy beta(-) emitter (1.07 MeV (95.9%)) with a half-life of 2.21 days. Pm-149 also emits a low abundance of an imageable gamma ray (286 keV (3%)) that may allow in vivo tracking of the therapeutic dose. The 149Pm and Sm complexes with the DO3A-amide chelator with zero and three carbon spacers to the bombesin peptide analog BBN(7-14)NH(2) were synthesized and characterized. The Sm complexes were synthesized for macroscopic characterization purposes (ESI-MS, in vitro cell binding) since no stable isotopes of Pm are known. The biological properties of the 149Pm, 153Sm and 177Lu-DO3A-amide-betaAla-BBN complexes were compared in normal mouse biodistribution studies.

Molecular basis of perinatal changes in UDP-glucuronosyltransferase activity in maternal rat liver

The molecular basis of perinatal changes occurring in major UDP-glucuronosyltransferase (UGT) family 1 isoforms and in UGT2B1, a relevant isoform belonging to family 2, was analyzed in rat liver. Nonpregnant, pregnant (19-20 days of pregnancy), and two groups of postpartum animals corresponding to early and middle stages of lactation (2-4 and 10-12 days after delivery, respectively) were studied. UGT activity determined in UDP-N-acetylglucosamine-activated microsomes revealed that bilirubin, p-nitrophenol, and ethynylestradiol (17beta-OH and 3-OH) but not androsterone and estrone glucuronidation rates, were decreased in pregnant rats. Decreased enzyme activities returned to control values after delivery. p-Nitrophenol, androsterone, and estrone conjugation rate increased in postpartum rats. Western blot analysis performed with anti-peptide-specific (anti-1A1, 1A5, 1A6, and 2B1) antibodies revealed decreased levels of all family 1 isoforms and UGT2B1 during pregnancy. In postpartum animals, protein level recovered (1A5 and 2B1) or even increased (1A1 and 1A6) with respect to control rats. Northern blot analysis suggested that expression of UGT proteins is down-regulated at a post-translational level during pregnancy and that increased levels of 1A1 and 1A6 observed in postpartum rats were associated to increased mRNA. To establish whether prolactin is involved in up-regulation of UGT1A1 and 1A6 postpartum, ovariectomized rats were treated with 300 microg of ovine prolactin per day for 7 days. The data indicated that prolactin was able to increase expression of UGT1A6 (protein and mRNA) but not 1A1. Thus, prolactin is the likely mediator of the increased expression of UGT1A6 observed in maternal liver postpartum.

Expression of multidrug resistance-associated protein 2 in small intestine from pregnant and postpartum rats

We analyzed the expression of multidrug resistance-associated protein 2 (mrp2) in the small intestine of control female rats and in rats during late pregnancy (19-20 days of pregnancy) and lactation (2-4, 10-14, and 21 days after delivery). Western blot analysis was performed on brush-border membranes prepared from different regions of the small intestine. Expression of mrp2 was maximal in the proximal segments for all experimental groups, was preserved in pregnant rats, and increased by 100% in postpartum rats by late lactation with respect to control animals. Northern blot analysis of mrp2 mRNA revealed a positive correlation with protein levels. Transport of S-glutathione-dinitrophenol (DNP-SG) from the intestinal cell to the lumen was analyzed in the everted intestinal sac model. Secretion of DNP-SG was not altered in pregnant rats but increased in lactating animals by late lactation. Intestinal mrp2 mRNA, protein, and transport activity are increased in lactating rats, suggesting that this may represent an adaptive mechanism to minimize the toxicity of dietary xenobiotics in response to increased postpartum food consumption.

Genitourinary tuberculosis after renal transplantation: report of 3 cases and review

Mycobacterium tuberculosis infection of the genitourinary tract is an uncommon disease in renal transplant recipients and presentation is atypical. Genitourinary tuberculosis is associated with graft rejection, and this diagnosis should be considered for renal transplant recipients with unexplained fever and constitutional symptoms.

Development of an in vitro model for assessing the in vivo stability of lanthanide chelates

An in vitro model was developed to evaluate the in vivo stability of lanthanide polyaminocarboxylate complexes. The ligand-to-metal ratios for the chelates EDTA, CDTA, DTPA, MA-DTPA (monoamide-DTPA) and DOTA with the lanthanides lanthanum, samarium, and lutetium were optimized to achieve > or = 98% complexation yield for the resultant radiolanthanide complexes. The exchange of the radiolanthanides from their EDTA, CDTA, DTPA, MA-DTPA and DOTA complexes with Ca(2+) was determined by in vitro adsorption and in vitro column studies using hydroxyapatite (HA), an in vitro bone model. In vitro serum stability of these radiolanthanide complexes was used as an additional indicator of in vivo stability, although the mechanism of instability in serum will be different than with bone. The in vitro studies were consistent with the expected findings that the smallest lanthanide (Lu) formed the most stable complexes. In vivo studies were done to validate the in vitro model. Biodistribution studies in normal CF-1 mice showed that in vivo stability of the complex (i.e., the more lanthanide remaining in complex form) could be assessed by a combination of the urinary, bone and liver uptake. For example, biodistribution studies demonstrate that high urinary excretion correlated with complex stability, while high liver plus bone uptake correlated with complex instability. The urinary excretion of the EDTA complexes decreased from (177)Lu to (140)La indicating a loss in stability in the direction of (140)La, consistent with the in vitro studies. The more stable a lanthanide complex is, the lower its exchange with HA in vitro will be, and the lower its combined bone plus liver uptake and higher its urinary excretion will be in vivo. This investigation indicates that the in vivo stability can be determined by a screening method that measures the degree of exchange from the lanthanide chelate with hydroxyapatite (HA) and its serum stability.

Differential regulation of hepatic bile salt and organic anion transporters in pregnant and postpartum rats and the role of prolactin

We characterized expression and activity of the bile salt transporters Na(+)/taurocholate (TC) cotransporting polypeptide (Ntcp), and bile salt export pump (Bsep), and the expression of organic anion transporting polypeptides 1 and 2 (Oatp1 and 2) and multidrug resistance associated protein-2 (Mrp2) in pregnancy and throughout lactation in rats. The V(max) for Na(+)/TC cotransport in basolateral liver plasma membrane was increased 1.7-fold in 2 days postpartum relative to control and pregnant rats. This correlated well with an increase in Ntcp messenger RNA (mRNA) and a 2-fold increase in Ntcp protein. Ntcp mRNA remained significantly elevated until 14 days postpartum but had begun to decline by 21 days postpartum. The maximal secretory rate (nmol/min/g liver) for TC in the single pass isolated perfused liver was also increased by 10%, 31%, and 24% at 2, 14, and 21 days postpartum and correlated with increased expression of Ntcp and Bsep mRNA and protein. Infusion of ovine prolactin (oPRL) to ovariectomized rats increased expression of both Ntcp and Bsep mRNA and protein. These data indicate a coordinate increased expression of bile salt transporters postpartum and by PRL. Mrp2 mRNA was stable in pregnancy and postpartum, whereas Mrp2 protein expression decreased significantly in pregnancy, but returned to control levels postpartum. Organic anion transporting polypeptide 2 (Oatp2) mRNA was decreased in pregnancy and increased postpartum, but changes in Oatp2 protein were not significant. Oatp1 mRNA and protein were unchanged in pregnancy and postpartum.

Expression and localization of multidrug resistant protein mrp2 in rat small intestine

The expression of multidrug resistance-associated protein isoform 2 (mrp2), the ATP-dependent export pump that mediates the transport of glucuronic acid-, glutathione-, and sulfate-conjugated derivatives, was studied in rat small intestine. The small intestine was divided into nine equal segments, and mrp2 content was analyzed in homogenate and brush border membrane preparations by Western analysis. mrp2 protein was present mainly in brush border membrane of the proximal segments and gradually decreased from jejunum to the distal ileum. We also analyzed the content of mrp2 in three different populations of proximal enterocytes obtained from the upper and lower villus and the crypt regions. The export pump was mainly expressed in the villus cells and to a lesser degree in the crypt cells of the epithelium. Immunohistochemical analysis performed in duodenum, jejunum, and ileum confirmed in situ the Western blot findings. Analysis of mRNA encoding mrp2 in proximal and distal segments revealed a similar content in both regions, whereas distribution along the villus-crypt axis was similar to the protein gradient. Because conjugating enzymes are distributed similarly to mrp2, we conclude that they may act coordinately to contribute to first-pass metabolism of drugs and other xenobiotics in the proximal small intestine.

Isolation of ethylene-insensitive soybean mutants that are altered in pathogen susceptibility and gene-for-gene disease resistance

Plants commonly respond to pathogen infection by increasing ethylene production, but it is not clear if this ethylene does more to promote disease susceptibility or disease resistance. Ethylene production and/or responsiveness can be altered by genetic manipulation. The present study used mutagenesis to identify soybean (Glycine max L. Merr.) lines with reduced sensitivity to ethylene. Two new genetic loci were identified, Etr1 and Etr2. Mutants were compared with isogenic wild-type parents for their response to different soybean pathogens. Plant lines with reduced ethylene sensitivity developed similar or less-severe disease symptoms in response to virulent Pseudomonas syringae pv glycinea and Phytophthora sojae, but some of the mutants developed similar or more-severe symptoms in response to Septoria glycines and Rhizoctonia solani. Gene-for-gene resistance against P. syringae expressing avrRpt2 remained effective, but Rps1-k-mediated resistance against P. sojae races 4 and 7 was disrupted in the strong ethylene-insensitive etr1-1 mutant. Rps1-k-mediated resistance against P. sojae race 1 remained effective, suggesting that the Rps1-k locus may encode more than one gene for disease resistance. Overall, our results suggest that reduced ethylene sensitivity can be beneficial against some pathogens but deleterious to resistance against other pathogens.

Adenosine triphosphate-dependent transport of estradiol-17beta(beta-D-glucuronide) in membrane vesicles by MDR1 expressed in insect cells

MDR1, an ABC transporter that confers multidrug resistance in tumor cells, is constitutively expressed in normal liver canalicular membrane. Human MDR1-expressing multidrug-resistant cells display increased resistance to estradiol-17beta(beta-D-glucuronide) (E217G). MDR1 substrates/modulators inhibit adenosine triphosphate (ATP)-dependent transport of E217G in the rat canalicular membrane and protect against E217G-mediated cholestasis in isolated perfused rat liver. The present studies were designed to determine if E217G is a substrate for MDR1 using a baculovirus expression system and if other estrogen glucuronides interact with MDR1. ATP-dependent transport of E217G (10 micromol/L) was linear for up to 2 minutes and yielded a rate of 45.6 pmol/min/mg protein in membrane vesicles from Sf9 cells infected with MDR1-baculovirus. This transport was saturable (Km = 62 micromol/L) and occurred into an osmotically sensitive space. ATP-dependent transport of E217G (10 micromol/L) was inhibited 63% by 10 micromol/L daunomycin, but not by 100 micromol/L S-(2,4-dinitrophenyl)glutathione (GS-DNP) (a substrate for canalicular multispecific organic anion transporter [cMOAT]). Glucuronide conjugates of the estrogen D-ring (100 micromol/L), estriol-17beta(beta-D-glucuronide) (E317G) and estriol-16(beta-D-glucuronide) (E316G), inhibited MDR1-mediated E217G transport by 58% and 35%, respectively. In contrast, noncholestatic glucuronides, estradiol-3-(beta-D-glucuronide) (E23G) or estradiol-3-sulfate-17beta(beta-D-glucuronide) (E23SO417G), had no effect. E217G neither stimulated MDR1 ATPase activity nor inhibited verapamil-stimulated ATPase activity. Infusion of 1.5 micromol/L doxorubicin or 1 micromol/L taxol protected against cholestasis induced by E316G and E317G in isolated perfused rat liver. These studies identify E217G, and probably E316G and E317G, as endogenous substrates for MDR1.

ATP-dependent transport of beta-estradiol 17-(beta-D-glucuronide) in rat canalicular membrane vesicles

The ATP-dependent transport of beta-estradiol 17-(beta-D-glucuronide) (E217G), a cholestatic metabolite of estradiol, was investigated in rat liver canalicular membrane vesicles. ATP-dependent transport was dependent on time and temperature and occurred into an osmotically sensitive space; kinetic analysis indicated a saturable transport system (Michaelis-Menten constant value, 75 microM; maximum transport rate, 598 pmol.min-1.mg protein-1). The steroid conjugates estradiol glucuronide, estriol 3-glucuronide, estriol 16 alpha-glucuronide, testosterone glucuronide, and the three-sulfate conjugate of 17G were effective inhibitors of transport. Bromosulfophthalein, S-(2,4-dinitrophenyl)glutathione, and glutathione disulfide, all substrates of the canalicular ATP-dependent non-bile acid organic anion transport system, were also effective inhibitors, whereas taurocholate had no effect on transport. Conversely, E217G inhibited the ATP-dependent transport of S-(2,4-dinitrophenyl)glutathione. Daunorubicin, vinblastine, etoposide, cyclosporin, and PSC-833, substrates/modulators of P-glycoprotein, were also potent inhibitors of E217G transport, and E217G competitively inhibited the ATP-dependent transport of daunorubicin. C219, a monoclonal antibody against P-glycoprotein, inhibited ATP-dependent transport of E217G and daunorubicin but not of taurocholate or S-(2,4-dinitrophenyl)glutathione. These data indicate that E217G is substrate of both the non-bile acid organic anion transport system and P-glycoprotein but not of the ATP-dependent bile acid transport system in canalicular membranes.

MDR1 substrates/modulators protect against beta-estradiol-17beta-D-glucuronide cholestasis in rat liver

beta-Estradiol 17beta-D-glucuronide (E(2)17G), an endogenous cholestatic metabolite of estradiol, has been identified as a substrate for both hepatic P-glycoprotein (P-gp) and the multispecific organic anion transporter (MOAT), the liver-specific homologue of the multidrug resistance protein. The aim of the present studies was to determine the role of hepatic P-gp and MOAT in E(2)17G-mediated cholestasis and its biliary excretion using the isolated perfused rat liver. A bolus dose of E(2)17G (2 micromol) alone decreased the bile flow maximally from 1.5 to 0.3 microl/min/g liver. In the presence of an infusion of 1.5 microM daunorubicin or 1.0 microM Taxol, P-gp substrates, E(2)17G cholestasis was blocked such that 2 micromol E(2)17G decreased the bile flow from 1.48 to 1.31 or from 1.70 to 1.31 microl/min/g liver, respectively. In the presence of 1 and 3 microM Taxol, the log dose-response curves for E(2)17G cholestasis were shifted to the right 2-fold and 5-fold, respectively, in a parallel manner. Taxol (10 and 50 microM) inhibited the ATP-dependent transport of 10 microM E(2)17G in canalicular plasma membrane vesicles by 46 and 81%, respectively. Daunorubicin (1.5 microM) also shifted the log dose-response curve for E(2)17G cholestasis to the right about 4-fold. Neither Taxol nor daunorubicin decreased the biliary excretion of E(2)17G. Infusion of cyclosporine (6 microM), an inhibitor of both P-gp and MOAT, significantly blocked both E(2)17G cholestasis and biliary excretion, such that 16 micromol E(2)17G decreased the bile flow only 15-20%. In contrast, bromosulfophthalein, a MOAT substrate, had no effect on either E(2)17G-mediated cholestasis or its biliary excretion. These data indicate that P-gp plays an essential role in E(2)17G-mediated cholestasis and suggest that MOAT functions to deliver high concentrations of E(2)17G to P-gp.

T cell leukemia-associated human Notch/translocation-associated Notch homologue has I kappa B-like activity and physically interacts with nuclear factor-kappa B proteins in T cells

Translocation-associated Notch homologue (TAN-1), a gene originally cloned from the translocation breakpoint of a human T cell leukemia carrying a 9:7(q34.3) translocation, encodes a protein belonging to the Notch/Lin-12/Glp-1 receptor family. These receptors mediate the specification of numerous cell fates during development in invertebrates and vertebrates. The intracellular portion of Notch/TAN-1 contains six ankyrin repeats that are similar to those found in cytoplasmic I kappa B proteins. I kappa B proteins are specific inhibitors of nuclear factor (NF)-kappa B/Rel transcription factors. Here we show that TAN-1 has functional properties of an I kappa B-like regulator with specificity for the NF-kappa B p50 subunit. A recombinant polypeptide corresponding to the cytoplasmic portion of TAN-1 (TAN-1C) specifically inhibited the DNA binding of p50-containing NF-kappa B complexes. When overexpressed in an appropriate cell line, TAN-1C prevented kappa B-dependent transactivation in transient reporter gene assays in a fashion similar to the structurally related protein, Bcl-3. TAN-1C could activate kappa B-dependent gene expression by attenuating the inhibitory effect of an excess of p50 homodimers. Immunoprecipitation experiments showed that the TAN-1 from a T cell line is associated with NF-kappa B containing p50 and p65 subunits. These observations indicate that TAN-1C may directly engage NF-kappa B transcription factors and modulate nuclear gene expression.