[Detection of EDA gene mutation and phenotypic analysis in patients with hypohidrotic ectodermal dysplasia].

OBJECTIVE: To detect the ectodysplasin A (EDA) gene mutation in patients with hypohidro-tic ectodermal dysplasia (HED), and to analyze the distribution pattern of missing permanent teeth and the systemic manifestation of HED patients with EDA gene mutation. METHODS: Twelve HED families were enrolled from clinic for genetic history collection, systemic physical examination and oral examination. Peripheral blood or saliva samples were collected from the probands and the family members to extract genomic DNA. PCR amplification and Sanger sequencing were utilized to detect the EDA gene variations, which were compared with the normal sequence (NM_001399.5). The functional impact of EDA gene variants was then evaluated by functional prediction of mutation, conservation analysis and protein structure prediction. The pathogenicity of each EDA gene variation was assessed according to the stan-dards and guidelines of the American College of Medical Genetics and Genomics (ACMG). The systemic phenotype and missing permanent tooth sites of HED patients with EDA gene mutations were summarized, and the missing rate of each tooth position was analyzed and compared. RESULTS: Eight out of twelve HED families were identified to carry EDA gene mutations, including: c.164T>C(p.Leu55Pro); c.457C>T (p.Arg153Cys); c.466C>T(p.Arg156Cys); c. 584G>A(p.Gly195Glu); c.619delG(p.Gly207Profs*73); c.673C>T(p.Pro225Ser); c.676C>T(p.Gln226*) and c.905T>G(p.Phe302Cys). Among them, c.164T>C(p.Leu55Pro); c.619delG(p.Gly207Profs*73); c.673C>T(p.Pro225Ser); c.676C>T(p.Gln226*) and c.905T>G(p.Phe302Cys) were novel mutations. The HED patients with EDA gene mutations in this study were all male. Our results showed that the average number of missing permanent teeth was 13.86±4.49, the average number of missing permanent teeth in the upper jaw was 13.14±5.76, the missing rate was 73.02%. And in the lower jaw, the average number of missing permanent teeth was 14.57±3.05, the missing rate was 80.95%. There was no significant difference in the number of missing teeth between the left and right sides of the permanent dentition (P>0.05). Specifi-cally, the maxillary lateral incisors, the maxillary second premolars and the mandibular lateral incisors were more likely to be missing, while the maxillary central incisors, the maxillary and mandibular first molars had higher possibility of persistence. CONCLUSION: This study detected novel EDA gene pathogenic variants and summarized the distribution pattern of missing permanent teeth of HED patients, thus enriched the variation and phenotype spectrum of EDA gene, and provided new clinical evidence for genetic diagnosis and prenatal consultation.

Antiviral response and resistance analysis of treatment-naïve HCV-infected patients receiving single and multiple doses of GS-9190.

GS-9190 is a NS5B non-nucleoside analogue with demonstrated effectiveness in a Phase 1 monotherapy study and in combination with other DAAs for treatment of chronic HCV infection. Here, the resistance profile of GS-9190 monotherapy in a Phase 1b study was investigated. Resistance analysis was performed by population sequencing and allele-specific PCR (AS-PCR) for Y448H with an assay cut-off of 0.5%. Phenotypic susceptibility analyses were performed on patient isolates as well as site-directed mutagenesis of mutations selected during monotherapy. No resistance-associated variants were observed in patients before or after receiving single doses of GS-9190 by population sequencing. In contrast, in patients who received GS-9190 for 8 days, mutations Y448H and Y452H in NS5B were observed by population sequencing in 21/36 (58%) and 2/36 (5.6%) patients, respectively, at Day 8 or Day 14. Among the remaining 15 patients who had no detectable Y448H at Day 8 or Day 14 by population sequencing, low frequencies of Y448H ranging from 1.3 to 9.7% were detected in 14 of 15 patients by AS-PCR. By AS-PCR, Y448H remained detectable at reduced frequency in the majority of patients analysed through 4-6 months of follow-up. Chimeric HCV replicons constructed with the NS5B sequence from patients with Y448H and Y448H + Y452H/Y demonstrated 27-fold and 78.5-fold reduced susceptibility to GS-9190. In conclusion, Y448H was rapidly selected in the majority of patients receiving multiple doses of GS-9190 as monotherapy, despite undetectable levels in pretreatment samples. Y448H confers reduced susceptibility to GS-9190 and other NNIs and persisted in most patients for months post-treatment.

Retraction RETRACTION of "Efficacy and safety of nucleoside analogues in preventing vertical transmission of the hepatitis B virus from father to infant", by L.-H. Cao, P.-L. Zhao, Z.-M. Liu, S.-C. Sun, D.-B. Xu, J.-D. Zhang and Z.-H. Shao - Genet. Mol. Res. 14 (4): 15539-15546 (2015).

The retracted article is: Cao L-H, Zhao P-L, Liu Z-M, Sun S-C, et al. (2015). Efficacy and safety of nucleoside analogues in preventing vertical transmission of the hepatitis B virus from father to infant. Genet. Mol. Res. 14: 15539-15546. The article published in Genetics and Molecular Research 14 (4): 15539-15546 (2015) is a very good paper, but it appears that the authors' group submitted this manuscript to multiple journals, which is ethical misconduct. This manuscript (similar language and identical data) was published in the Experimental and Therapeutic Medicine Journal prior to being submitted to GMR. There are parts copied from "Efficacy and safety of nucleoside analogs on blocking father-to-infant vertical transmission of hepatitis B virus", by Li-Hau Cao, Pei-Li Zhao, Zhi-Min Liu, Shao-Chun Sun, et al. Exp. Ther. Med. 9 (6): 2251-2256 (2015) - DOI: 10.3892/etm.2015.2379. The GMR editorial staff was alerted and after a thorough investigation, there is strong reason to believe that the peer review process was failure. Also, after review and contacting the authors, the editors of Genetics and Molecular Research decided to retract this article in accordance with the recommendations of the Committee on Publication Ethics (COPE). The authors and their institutions were advised of this serious breach of ethics.

Efficacy and safety of nucleoside analogues in preventing vertical transmission of the hepatitis B virus from father to infant.

We examined the efficacy and safety of nucleoside analogues in preventing the vertical transmission of hepatitis B virus (HBV) from father to infant. We included 201 patients who visited the liver clinic of our hospital. The patients were positive for HBV surface antigen (HBsAg), HBeAg, anti-HBc, and HBV DNA; 189 patients (94%) had abnormal liver function. In all couples, the fathers were HBV DNA-negative and had normal liver function, and the mothers were anti-HB-positive before pregnancy. The control group comprised 188 couples who visited our hospital during the same time period. The fathers in the control group were positive for HBsAg, HBeAg, anti-HBc, and HBV DNA. The mothers were HBsAg-negative and anti-HBs-positive. No infants in the case group were HBsAg-positive and HBV DNA-positive, and all were anti-HBs-positive, indicating that father to infant HBV vertical transmission was prevented in the case group. In the control group, 147 of 188 newborns (78.2%) were anti-HBs-positive at birth, 28 (14.9%) were HBV DNA-positive, and 19 (10.1%) were HBsAg-positive. A significant difference was observed between the two groups. No statistically significant difference was observed in the gestational age, birth weight, birth length, 1-min and 8-min Apgar score, jaundice, other internal and surgical diseases, delivery mode, and other birth information between the neonates born to couples in the case and control groups; there were no fetal malformations and stillbirths in the two groups. Our results showed that administration of antiretroviral therapy to HBV DNA-positive fathers before pregnancy can cause a decrease in the viral load and prevent father to infant HBV vertical transmission. The use of antiviral nucleoside analogues before pregnancy was safe in fathers, and the fathers who wanted children could continue to use anti-viral therapy. The sample size in our study was small, and further studies with a large sample size and longer follow-up time are required for determining the use of nucleoside analogues from the point view of prenatal and postnatal care.

Proteomic analysis revealed the altered kidney protein profile of a Cyld knockout mouse model.

The aim of this study was to compare the proteomics pattern of the kidneys from Cyld knockout mice with that from normal mouse kidneys and establish a preliminary understanding of the role of Cyld in the kidney. Proteins from the kidneys of knockout Cyld mice and wild-type mice were extracted, isobaric tags for relative and absolute quantitation (iTRAQ) was performed, and the proteomics patterns of the two groups were compared. The genotypes of the mice were verified by polymerase chain reaction. A total of 1748 proteins with a local false discovery rate of ≤5% were identified, among which 1437 proteins were reliably recognized and quantified. The expression of two dysregulated proteins was confirmed by Western blotting. Gene ontology and pathway analyses indicated that the proteins identified were involved in biological processes, cell components, and molecular functions, and participated in different pathways. Some of the proteins identified were relevant to renal function or kidney diseases. The difference between the proteomics profiles of kidneys from Cyld knockout mice and wild-type mice was prominent, which correlates to kidney dysfunction and the development of renal diseases.

Efficacy of combined hepatitis B immunoglobulin and hepatitis B vaccine in blocking father-infant transmission of hepatitis B viral infection.

The aim of this study was to examine the efficacy of combined immunization of hepatitis B immunoglobulin (HBIG) and hepatitis B vaccine (HBVac) in blocking father-infant transmission of hepatitis B virus (HBV). Newborns positive at birth for blood HBV sur-face antigen (HBsAg) and/or HBV DNA were selected and immunized with HBIG combination HBVac. At 7 months, HBV markers and HBV DNA of each neonate were measured using electrochemiluminescence with the Cobas-e-411 Automatic Electrochemiluminescence Immuno-assay Analyzer and fluorescence quantitative polymerase chain reaction. Among all 7-month-old subjects, the negative conversion rates of HBV DNA and HBsAg were 48/61 (78.7%) and 19/41 (46.3%), respectively. Therefore, this study demonstrated that prompt combination injection of HBIG and HBVac can protect some of the HBV DNA- and/ or HBsAg-positive newborns from HBV.

Natural variation in drug susceptibility to HCV polymerase inhibitors in treatment-naïve HCV patient isolates.

Summary. To assess the natural variation in drug susceptibility among treatment-naïve hepatitis C virus (HCV) patient isolates, the susceptibilities of chimeric replicons carrying the HCV NS5B polymerase from up to 51 patient isolates against a panel of diverse HCV nonnucleoside polymerase inhibitors were evaluated using a replicon-based transient replication assay. Some patient to patient variation in susceptibility to the panel of three HCV nonnucleoside polymerase inhibitors was observed. Linear regression and correlation analyses revealed no correlations among the susceptibilities to the polymerase inhibitors tested. Our results suggest that variable antiviral responses to HCV nonnucleoside polymerase inhibitors may be observed because of the natural variation in baseline susceptibility. In addition, the lack of correlation among the susceptibilities to three classes of HCV polymerase inhibitors evaluated here supports their possible combined use in a combination therapy strategy.

Estimation of inhibitory quotient using a comparative equilibrium dialysis assay for prediction of viral response to hepatitis C virus inhibitors.

The relationship of inhibitory quotient (IQ) with the virologic response to specific inhibitors of human hepatitis C virus (HCV) and the best method to correct for serum protein binding in calculating IQ have not been addressed. A common method is to determine a fold shift by comparing the EC(50) values determined in cell culture in the absence and presence of human serum (fold shift in EC(50) ), but this method has a number of disadvantages. In the present study, the fold shifts in drug concentrations between 100% human plasma (HP) and cell culture medium (CCM) were directly measured using a modified comparative equilibrium dialysis (CED) assay for three HCV protease inhibitors (PIs) and for a novel HCV inhibitor GS-9132. The fold shift values in drug concentration between the HP and CCM (CED ratio) were ∼1 for SCH-503034, VX-950 and GS-9132 and 13 for BILN-2061. These values were ∼3-10-fold lower than the fold shift values calculated from the EC(50) assay for all inhibitors except BILN-2061. Using the CED values, a consistent pharmacokinetic and pharmacodynamic relationship was observed for the four HCV inhibitors analysed. Specifically, an approximate 1 log(10) reduction in HCV RNA was achieved with an IQ close to 1, while 2-3 and greater log(10) reductions in HCV RNA were achieved with IQ values of 3-5 and greater, respectively. Thus, use of CED to define IQ provides a predictive and quantitative approach for the assessment of the in vivo potency of HCV PIs and GS-9132. This method provides a framework for the evaluation of other classes of drugs that are bound by serum proteins but require the presence of serum for in vitro evaluation.

Single nucleotide polymorphism analysis of exons 3 and 4 of IGF-1 gene in pigs.

The IGF-1 gene has been implicated as a candidate gene for the regulation of pig growth traits. We analyzed exons 3 and 4 of IGF-1 gene polymorphisms of the Banna mini-pig (28), the Tibetan mini-pig (30), the Junmu pig (55), and L. Yorkshire species (50) using PCR-SSCP. Three genotypes in exon 3 and 6 genotypes in exon 4 were observed, among which, one single nucleotide polymorphism, G201A, on exon 3 and two single nucleotide polymorphisms, A440G and T455C, on exon 4 were found. Statistical analysis of genotype frequencies revealed that the A allele was dominant in the large pig at the G201A locus (PIC = 0.20-0.34), and the AT alleles were dominant in the large pig at the A440G and T455C loci (PIC = 0.30-0.60). The genotype distribution between the various groups was significantly different (P< 0.01), with the highest heterozygosity seen in Junmu pigs at 0.223 and the lowest seen in L. Yorkshire at 0.098. The genetic distance of the Junmu pig from the L. Yorkshire is the smallest, the distance from the Tibetan miniature pigs is larger, and the distance from the Banna mini-pig is the largest. The IGF-1 gene polymorphism and heterozygosity results from various pig breeds indicate that IGF-1 is substantially polymorphic with significant difference of the polymorphic distribution and expression levels among various pig breeds. This information provides a theoretical basis for the genetic background of miniature pigs but also provides means to breed improved pig varieties.

Band-selective Holstein polaron in Luttinger liquid material A0.3MoO3 (A = K, Rb).

(Quasi-)one-dimensional systems exhibit various fascinating properties such as Luttinger liquid behavior, Peierls transition, novel topological phases, and the accommodation of unique quasiparticles (e.g., spinon, holon, and soliton, etc.). Here we study molybdenum blue bronze A0.3MoO3 (A = K, Rb), a canonical quasi-one-dimensional charge-density-wave material, using laser-based angle-resolved photoemission spectroscopy. Our experiment suggests that the normal phase of A0.3MoO3 is a prototypical Luttinger liquid, from which the charge-density-wave emerges with decreasing temperature. Prominently, we observe strong renormalizations of band dispersions, which are recognized as the spectral function of Holstein polaron derived from band-selective electron-phonon coupling in the system. We argue that the strong electron-phonon coupling plays an important role in electronic properties and the charge-density-wave transition in blue bronzes. Our results not only reconcile the long-standing heavy debates on the electronic properties of blue bronzes but also provide a rare platform to study interesting excitations in Luttinger liquid materials.

NF-kappa B controls expression of inhibitor I kappa B alpha: evidence for an inducible autoregulatory pathway.

The eukaryotic transcription factor nuclear factor-kappa B (NF-kappa B) participates in many parts of the genetic program mediating T lymphocyte activation and growth. Nuclear expression of NF-kappa B occurs after its induced dissociation from its cytoplasmic inhibitor I kappa B alpha. Phorbol ester and tumor necrosis factor-alpha induction of nuclear NF-kappa B is associated with both the degradation of performed I kappa B alpha and the activation of I kappa B alpha gene expression. Transfection studies indicate that the I kappa B alpha gene is specifically induced by the 65-kilodalton transactivating subunit of NF-kappa B. Association of the newly synthesized I kappa B alpha with p65 restores intracellular inhibition of NF-kappa B DNA binding activity and prolongs the survival of this labile inhibitor. Together, these results show that NF-kappa B controls the expression of I kappa B alpha by means of an inducible autoregulatory pathway.

Hemolin: an insect-immune protein belonging to the immunoglobulin superfamily.

Insects have an efficient defense system against infections. Their antibacterial immune proteins have been well characterized. However, the molecular mechanisms by which insects recognize foreignness are not yet known. Data are presented showing that hemolin (previously named P4), a bacteria-inducible hemolymph protein of the giant silk moth Hyalophora cecropia, belongs to the immunoglobulin superfamily. Functional analyses indicate that hemolin is one of the first hemolymph components to bind to the bacterial surface, taking part in a protein complex formation that is likely to initiate the immune response.

Endocarditis in mice infected with Coxsackie virus B4.

Endocarditis has not been generally considered to be a complication of viral infection. We show that mural and valvular endocarditis can be produced in mice infected with Coxsackie virus B(4). Because this virus commonly infects man and is highly cardiotropic, it is important to know whether it produces valvular lesions in man similar to those we describe in mice.

Activation by IKKalpha of a second, evolutionary conserved, NF-kappa B signaling pathway.

In mammals, the canonical nuclear factor kappaB (NF-kappaB) signaling pathway activated in response to infections is based on degradation of IkappaB inhibitors. This pathway depends on the IkappaB kinase (IKK), which contains two catalytic subunits, IKKalpha and IKKbeta. IKKbeta is essential for inducible IkappaB phosphorylation and degradation, whereas IKKalpha is not. Here we show that IKKalpha is required for B cell maturation, formation of secondary lymphoid organs, increased expression of certain NF-kappaB target genes, and processing of the NF-kappaB2 (p100) precursor. IKKalpha preferentially phosphorylates NF-kappaB2, and this activity requires its phosphorylation by upstream kinases, one of which may be NF-kappaB-inducing kinase (NIK). IKKalpha is therefore a pivotal component of a second NF-kappaB activation pathway based on regulated NF-kappaB2 processing rather than IkappaB degradation.

Distal trisomy of 10q with distal monosomy of 15q due to a paternal translocation.

Distal trisomy of 10q is a rare chromosomal abnormality. Distal deletions of the terminal long arm of chromosome 15 have rarely been described. We report on a male infant with low birth weight and microcephaly, a flat face with a spacious forehead, low-set ears, blepharophimosis, microphthalmia, a small nose, and a depressed nasal bridge. Microarray comparative genomic hybridization identified that he had the karyotype 46, XY, der (15) t (10;15) (q25.2;q26.2) pat, with chromosomal breakpoints at 10q25.2 and 15q26.2. This male neonatal case had an unbalanced translocation inherited from his father who was a balanced carrier with the karyotype 46, XY, t (10;15) (q25;q26). The neonate had a partial trisomy of the long arm of chromosome 10 with a partial monosomy of distal 15q. The clinical features were in agreement with previous descriptions and allowed us to propose a growth retardation phenotype for this neonate case.

Ground-to-satellite time and frequency synchronization link with active carrier phase compensation.

In this paper, a synchronization link between one ground station and one geostationary satellite is established. The ground station receives retransmitted signals from the satellite, measures phase delay along the propagation route, and actively compensates back to its sending signals, realizing real-time phase fluctuation compensation. The transmitted signal contains two frequencies to eliminate common-mode phase noise. The difference between their carrier phase delays is measured. Different modes of carrier phase variation are separated and compensated, achieving a remaining time jitter of ±200 ps. Major sources of error are analyzed, and potential methods for improvement are discussed. The proposed ground-to-satellite link and active compensation method has potential applications in frequency standard dissemination to remote receivers (including ground stations or satellites). These potential applications justify further study of this system.

Species-specific in vitro pharmacological effects of the cannabinoid receptor 2 (CB2) selective ligand AM1241 and its resolved enantiomers.

BACKGROUND AND PURPOSE: Racemic (R,S) AM1241 is a cannabinoid receptor 2 (CB(2))-selective aminoalkylindole with antinociceptive efficacy in animal pain models. The purpose of our studies was to provide a characterization of R,S-AM1241 and its resolved enantiomers in vitro and in vivo. EXPERIMENTAL APPROACH: Competition binding assays were performed using membranes from cell lines expressing recombinant human, rat, and mouse CB(2) receptors. Inhibition of cAMP was assayed using intact CB(2)-expressing cells. A mouse model of visceral pain (para-phenylquinone, PPQ) and a rat model of acute inflammatory pain (carrageenan) were employed to characterize the compounds in vivo. KEY RESULTS: In cAMP inhibition assays, R,S-AM1241 was found to be an agonist at human CB(2), but an inverse agonist at rat and mouse CB(2) receptors. R-AM1241 bound with more than 40-fold higher affinity than S-AM1241, to all three CB(2) receptors and displayed a functional profile similar to that of the racemate. In contrast, S-AM1241 was an agonist at all three CB(2) receptors. In pain models, S-AM1241 was more efficacious than either R-AM1241 or the racemate. Antagonist blockade demonstrated that the in vivo effects of S-AM1241 were mediated by CB(2) receptors. CONCLUSIONS AND IMPLICATIONS: These findings constitute the first in vitro functional assessment of R,S-AM1241 at rodent CB(2) receptors and the first characterization of the AM1241 enantiomers in recombinant cell systems and in vivo. The greater antinociceptive efficacy of S-AM1241, the functional CB(2) agonist enantiomer of AM1241, is consistent with previous observations that CB(2) agonists are effective in relief of pain.

Regulation of RelA subcellular localization by a putative nuclear export signal and p50.

Nuclear factor kappaB (NF-kappaB) represents a family of dimeric DNA binding proteins, the pleotropic form of which is a heterodimer composed of RelA and p50 subunits. The biological activity of NF-kappaB is controlled through its subcellular localization. Inactive NF-kappaB is sequestered in the cytoplasm by physical interaction with an inhibitor, IkappaBalpha. Signal-mediated IkappaBalpha degradation triggers the release and subsequent nuclear translocation of NF-kappaB. It remains unknown whether the NF-kappaB shuttling between the cytoplasm and nucleus is subjected to additional steps of regulation. In this study, we demonstrated that the RelA subunit of NF-kappaB exhibits strong cytoplasmic localization activity even in the absence of IkappaBalpha inhibition. The cytoplasmic distribution of RelA is largely mediated by a leucine-rich sequence homologous to the recently characterized nuclear export signal (NES). This putative NES is both required and sufficient to mediate cytoplasmic localization of RelA as well as that of heterologous proteins. Furthermore, the cytoplasmic distribution of RelA is sensitive to a nuclear export inhibitor, leptomycin B, suggesting that RelA undergoes continuous nuclear export. Interestingly, expression of p50 prevents the cytoplasmic expression of RelA, leading to the nuclear accumulation of both RelA and p50. Together, these results suggest that the nuclear and cytoplasmic shuttling of RelA is regulated by both an intrinsic NES-like sequence and the p50 subunit of NF-kappaB.

Regulation of the interleukin-2 CD28-responsive element by NF-ATp and various NF-kappaB/Rel transcription factors.

The CD28 costimulatory signal enhances antigen-mediated induction of interleukin-2 (IL-2) gene transcription through activation of an enhancer termed the CD28-responsive element (CD28RE). Although various nuclear proteins have been shown to bind to CD28RE, their in vivo functions in the regulation of this enhancer remain elusive. In this report, we show that CD28RE binds distinct transcription factors in cells treated with different mitogenic stimuli. Stimulation of the T-cell receptor (TCR) complex in the absence of a CD28 costimulatory signal induces a member of the nuclear factor of the activated T cells, NF-ATp; however, this treatment fails to activate the CD28RE enhancer activity. Significant activation of CD28RE was detected when the cells were treated with both the TCR stimulators and an anti-CD28 monoclonal antibody (anti-CD28), which induces the NF-kappaB/Rel enhancer binding proteins in addition to NF-ATp. The costimulatory activity of anti-CD28 can be further enhanced by a phorbol ester. Kinetic analyses demonstrate that activation of endogenous IL-2 gene transcription is correlated with the binding of CD28RE by NF-ATp and different NF-kappaB/Rel species. Transient-transfection studies reveal that expression of either NF-ATp or the p50-RelA NF-kappaB heterodimer leads to the potent transactivation of both the CD28RE enhancer and the intact IL-2 promoter in mitogen-stimulated cells. Remarkably, coexpression of these two families of enhancer-binding proteins in Jurkat T cells results in the transactivation of the CD28RE enhancer even in the absence of any cellular stimuli. Together, these results suggest that activation of IL-2 gene transcription by the TCR- and CD28-mediated signals involves the interaction of CD28RE with NF-ATp and various NF-kappaB/Rel transcription factors.

A novel NF-kappa B complex containing p65 homodimers: implications for transcriptional control at the level of subunit dimerization.

The predominant inducible form of the NF-kappa B transcription factor is a heteromeric complex containing two Rel-related DNA-binding subunits, termed p65 and p50. Prior transfection studies have shown that when these p65 and p50 subunits are expressed independently as stable homodimers, p65 stimulates kappa B-directed transcription, whereas p50 functions as a kappa B-specific repressor. While authentic p50 homodimers (previously termed KBF1) have been detected in nuclear extracts from nontransfected cells, experimental evidence supporting the existence of p65 homodimers in vivo was lacking. We now provide direct biochemical evidence for the presence of an endogenous pool of inducible p65 homodimers in intact human T cells. As with the prototypical NF-kappa B p50-p65 heterodimer, this novel p65 homodimeric form of NF-kappa B is functionally sequestered in the cytoplasm but rapidly appears in the nuclear compartment following cellular stimulation. Site-directed mutagenesis studies indicate that the homodimerization function of p65 is dependent upon the presence of cysteine 216 and a conserved recognition motif for protein kinase A (RRPS; amino acids 273 to 276), both of which reside within a 91-amino-acid segment of the Rel homology domain that mediates self-association. In contrast, mutations at these two sites do not affect heterodimerization of p65 with p50 or its functional interaction with I kappa B alpha. These later findings indicate that neither homo- nor heterodimer formation is an absolute prerequisite for I kappa B alpha recognition of p65. Taken together with prior in vivo transcription studies, these results suggest that the biological activities of p65 and p50 homodimers are independently regulated, thereby providing an integrated and flexible control mechanism for the rapid activation and repression of NF-kappa B/Rel-directed gene expression.