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Biomedical subjects

E S Reddy

Publications and source records attributed to E S Reddy.

48 records · Page 3Linked to original sources
PubMed1983

Inhibition of reverse transcriptases by seminalplasmin.

Seminalplasmin, an antibacterial protein present in bovine seminal plasma, is shown to be a potent inhibitor of reverse transcriptases (RNA-dependent DNA nucleotidyltransferases). Seminalplasmin inhibits RNA-directed, hybrid-directed, and DNA-directed DNA-polymerizing activities of purified reverse transcriptase from avian myeloblastosis virus and from crude viral lysates of several retroviruses by binding to the enzyme, at least in the case of avian myeloblastosis virus. Seminalplasmin does not inhibit significantly DNA synthesis either by Escherichia coli DNA polymerase I, or a mammalian alpha-DNA polymerase. The presence of seminalplasmin in the seminal fluid could provide protection to the male and/or the female reproductive tract against retroviruses.

Avian Myeloblastosis Virus↗
PubMed1983

Effect of spermine, ethylenediamine tetraacetate, urea, and high salt on the activity of ribonuclease SPL on Mg2+- containing undenatured total E. coli and rat liver RNAs.

Using RNAase SPL, a recently described nuclease from bovine seminal plasma, that can recognize certain Mg2+-dependent structural features in native naturally occurring RNAs, it is shown that these features are wholly or partially destroyed by 8 M urea, 1 mM spermine, 0.35 M KCl or NaCl, and 10 mM EDTA, urea and spermine being the most effective and EDTA the least; these features are not destroyed by heating and rapid cooling unless a medium with a high ionic strength is used. Since the buffer used so far for reconstitution of ribosomes contains 0.35 M KCl, it seems possible that a partial opening up of ribosomal RNAs may be necessary for ribosome assembly.

Animals↗
PubMed1982

Mouse interferons enhance the accumulation of a human HLA RNA and protein in transfected mouse and hamster cells.

A recombinant clone (pJY150R1.1) encoding the human major histocompatibility antigen (HLA-B7) was introduced into mouse cells and hamster cells by cotransformation with selectable genes. The exposure to mouse interferon of the cells transformed to HLA-B7+ resulted in a severalfold increase in the level of HLA antigen and RNA. The HLA-B7 clone used for the transfection includes a 670-base pair DNA sequence upstream from the coding segment. It remains to be established if the 670-base pair segment is necessary and/or sufficient to make the transcription of the HLA gene responsive to interferon.

Animals↗
PubMedDate not supplied

Ets-related protein Elk-1 is homologous to the c-fos regulatory factor p62TCF.

A key event in the response of cells to proliferative signals is the rapid, transient induction of the c-fos proto-oncogene, which is mediated through the serum response element (SRE) in the fos promoter. Genomic footprinting and transfection experiments suggest that this activation occurs through a ternary complex that includes the serum response factor (SRF) and the ternary complex factor p62. Interaction of p62TCF with the SRF-SRE binary complex requires a CAGGA tract immediately upstream of the SRE. Proteins of the ets proto-oncogene family bind to similar sequences and we have found that a member of this family, Elk-1, forms SRF-dependent ternary complexes with the SRE. Elk-1 and p62TCF have the same DNA sequence requirements and antibodies against Elk-1 block the binding of both proteins. Furthermore, we show that like p62TCF, Elk-1 forms complexes with the yeast SRF-homologue MCM1 but not with yeast ARG80. But ARG80 mutants that convey interaction with p62TCF can also form complexes with Elk-1. The similarity, or even identity, between Elk-1 and p62TCF suggests a novel regulatory role for Ets proteins that is effected through interaction with other proteins, such as SRF. Furthermore, the possible involvement of an Ets protein in the control of c-fos has interesting implications for proto-oncogene cooperation in cellular growth control.

Animals↗
PubMedDate not supplied

Differential transcriptional activation by the N-terminal region of BRCA1 splice variants BRCA1a and BRCA1b.

The breast and ovarian cancer susceptibility gene BRCA1, is a nuclear phosphoprotein which functions as a tumor suppressor in human breast cancer cells. BRCA1 protein contains an amino-terminal zinc finger motif and a carboxy-terminal acidic region. Recently, the carboxy-terminal region of BRCA1 and the amino-terminal region of BRCA2 proteins were shown to function as transactivation domains when fused to GAL4 DNA binding domain. We have recently isolated and characterized two new naturally occurring variants of BRCA1 (BRCA1a/p110 and BRCA1b/p100) which are phosphoproteins containing phosphotyrosine that associate with E2F transcriptional factors, cyclins and cyclin dependent kinases indicating a role for BRCA1 proteins in cell-cycle regulation. Here we show for the first time that the amino-terminal region of BRCA1a (BNT) but not BRCA1b can also function as a transcriptional activator when fused to GAL4 DNA binding domain. Thus, BRCA1/1a proteins contain two autonomous transcriptional activation domains, one at the amino-terminal region (BNT) and the other at the carboxy-terminal region (BCT). BRCA1b retains only the BCT domain since it has lost part of the potential BNT domain as a result of alternative splicing. Our results also suggest the presence of an inhibitory domain at the carboxy terminal region of BRCA1 and BRCA1a proteins (BID). Thus, BRCA1b protein may function as a dominant negative variant that could regulate the transcriptional activity of BRCA1/BRCA1a proteins and hence may serve as a marker for identifying individuals with greater potential for developing breast cancer. It may be possible that loss of transcriptional activation or protein-protein interactions in patients with mutations in the amino terminal zinc finger domain could deprive the cell of an important mechanism for regulating cell proliferation leading to the development of breast cancer.

3T3 Cells↗
PubMedDate not supplied

BRCA1 splice variants BRCA1a and BRCA1b associate with CBP co-activator.

The tumor suppressor gene BRCA1, is a nuclear phosphoprotein which associates with RNA polymerase II holoenzyme. CBP is a component of the holoenzyme. Previously, we have characterized two new BRCA1 splice variants BRCA1a/p110 and BRCA1b/p100. In the present study, the carboxy-terminal domain of transcription factor CBP interacts both in vivo and in vitro with full length BRCA1a and BRCA1b proteins as demonstrated by mammalian two- hybrid assays, co-immunoprecipitation/western blot studies, GST binding assays and histone acetyl transferase (HAT) assays of BRCA1 immunoprecipitates from human breast cancer cells. Our results suggest that one of the mechanisms by which BRCA1 proteins function is through recruitment of CBP associated HAT/FAT (transcription factor acetyl-transferase) activity for acetylation of either themselves or general transcription factors or both to specific promoters resulting in transcriptional activation.

Acetyltransferases↗
PubMedDate not supplied

Structure and expression of variant BRCA2a lacking the transactivation domain.

BRCA1 and BRCA2 are tumor suppressor genes shown to be involved in 90% of familial breast cancers and also known to be involved in ovarian and prostate cancers. Both BRCA1 and BRCA2 gene products are regulated in a cell cycle-dependent manner and have potential transactivation function. Here, we show that BRCA2 undergoes differential splicing giving rise to a novel variant protein BRCA2a, lacking putative transcriptional activation domain. Both BRCA2a and BRCA2 are expressed at high levels in thymus and testis but moderate levels in mammary gland and prostate suggesting that BRCA2a and BRCA2 may have a role in the development and differentiation of these tissues.

Alternative Splicing↗