Biomedical subjects

L A Chodosh

Publications and source records attributed to L A Chodosh.

16 recordsLinked to original sources

PubMed1998

BAP1: a novel ubiquitin hydrolase which binds to the BRCA1 RING finger and enhances BRCA1-mediated cell growth suppression.

We have identified a novel protein, BAP1, which binds to the RING finger domain of the Breast/Ovarian Cancer Susceptibility Gene product, BRCA1. BAP1 is a nuclear-localized, ubiquitin carboxy-terminal hydrolase, suggesting that deubiquitinating enzymes may play a role in BRCA1 function. BAP1 binds to the wild-type BRCA1-RING finger, but not to germline mutants of the BRCA1-RING finger found in breast cancer kindreds. BAP1 and BRCA1 are temporally and spatially co-expressed during murine breast development and remodeling, and show overlapping patterns of subnuclear distribution. BAP1 resides on human chromosome 3p21.3; intragenic homozygous rearrangements and deletions of BAP1 have been found in lung carcinoma cell lines. BAP1 enhances BRCA1-mediated inhibition of breast cancer cell growth and is the first nuclear-localized ubiquitin carboxy-terminal hydrolase to be identified. BAP1 may be a new tumor suppressor gene which functions in the BRCA1 growth control pathway.

Amino Acid Sequence↗

PubMed1997

Precocious mammary gland development in P-cadherin-deficient mice.

To investigate the functions of P-cadherin in vivo, we have mutated the gene encoding this cell adhesion receptor in mice. In contrast to E- and N-cadherin- deficient mice, mice homozygous for the P-cadherin mutation are viable. Although P-cadherin is expressed at high levels in the placenta, P-cadherin-null females are fertile. P-cadherin expression is localized to the myoepithelial cells surrounding the lumenal epithelial cells of the mammary gland. The role of the myoepithelium as a contractile tissue necessary for milk secretion is clear, but its function in the nonpregnant animal is unknown. The ability of the P-cadherin mutant female to nurse and maintain her litter indicates that the contractile function of the myoepithelium is not dependent on the cell adhesion molecule P-cadherin. The virgin P-cadherin-null females display precocious differentiation of the mammary gland. The alveolar-like buds in virgins resemble the glands of an early pregnant animal morphologically and biochemically (i.e., milk protein synthesis). The P-cadherin mutant mice develop hyperplasia and dysplasia of the mammary epithelium with age. In addition, abnormal lymphocyte infiltration was observed in the mammary glands of the mutant animals. These results indicate that P-cadherin-mediated adhesion and/or signals derived from cell-cell interactions are important determinants in negative growth control in the mammary gland. Furthermore, the loss of P-cadherin from the myoepithelium has uncovered a novel function for this tissue in maintaining the undifferentiated state of the underlying secretory epithelium.

Animals↗

PubMed1997

Developmental expression of Brca2 colocalizes with Brca1 and is associated with proliferation and differentiation in multiple tissues.

Germline mutations in the putative tumor suppressor gene, BRCA1, predispose women to dramatically elevated risks of breast cancer, while germline mutations in the structurally unrelated gene, BRCA2, predispose both men and women to breast cancer. Recent studies have suggested an important developmental role for the murine homologue of BRCA1 in the regulation of proliferation and differentiation. At the present time, however, little is known about the developmental role of BRCA2 or the regulation of its expression in vivo. We have determined the spatial and temporal pattern of expression of the murine homologue of BRCA2 during fetal development, in adult tissues, and in the mammary gland during postnatal development. Our results indicate that Brca2 mRNA expression is highest in proliferating cellular compartments, particularly those undergoing differentiation. In the breast, Brca2 expression is developmentally regulated and is induced during puberty and pregnancy and as a result of parity. Surprisingly, in multiple fetal and adult tissues the spatial and temporal pattern of Brca2 mRNA expression is virtually indistinguishable from that of Brca1, despite the fact that these genes display no homology. These observations suggest that Brca2 is involved in the processes of proliferation and differentiation in the mammary gland and other tissues, and that Brca1 and Brca2 mRNA expression may be regulated by similar pathways and stimuli in multiple cell types. Interestingly, however, our analysis reveals that Brca1 and Brca2 expression are differentially regulated during the development of specific endocrine target tissues, such as the testis during spermatogenesis and the breast during pregnancy. In addition, the ratio of mRNA expression in the mammary glands of adult females relative to adult males is significantly greater for Brca1 than for Brca2. These observations imply that Brca1 and Brca2 mRNA expression are differentially regulated by sex hormones. In order to test this hypothesis, we have analyzed the expression of these two breast cancer susceptibility genes in ovariectomized mice treated with 17beta-estradiol and progesterone. Our results demonstrate that the up-regulation of mRNA expression in the breast by ovarian hormones is significantly greater for Brca1 than for Brca2. These observations suggest that the gender-specific differences in phenotype associated with germline mutations in BRCA2 versus BRCA1 may be related to the differential regulation of these genes by sex hormones.

Animals↗

PubMed1996

Brca2 is coordinately regulated with Brca1 during proliferation and differentiation in mammary epithelial cells.

We have analyzed the expression of the breast cancer susceptibility gene, Brca2, in mammary epithelial cells as a function of proliferation and differentiation. Our results demonstrate that Brca2 mRNA expression is tightly regulated during mammary epithelial proliferation and differentiation, and that this regulation occurs coordinately with Brca1. Specifically, Brca2 mRNA expression is up-regulated in rapidly proliferating cells; is down-regulated in response to serum deprivation; is expressed in a cell cycle-dependent manner, peaking at the G1/S boundary; and is up-regulated in differentiating mammary epithelial cells in response to glucocorticoids. In each case, an identical pattern of expression was observed for Brca1. These results indicate that proliferative stimuli modulate the mRNA expression of these two breast cancer susceptibility genes. In addition, the coordinate regulation of Brca1 and Brca2 revealed by these experiments suggests that these genes are induced by, and may function in, overlapping regulatory pathways involved in the control of cell proliferation and differentiation.

Animals↗

PubMed1995

Play ball!

Explore the source record for details and available documents.

Baseball↗

PubMed1995

The developmental pattern of Brca1 expression implies a role in differentiation of the breast and other tissues.

We have examined the developmental expression of the murine breast and ovarian cancer susceptibility gene, Brca1, to investigate its role in the control of cell growth and differentiation. Specifically, we have analysed Brca1 expression during embryonic development, in adult tissues, and during postnatal mammary gland development, particularly in response to ovarian hormones. Our results suggest that Brca1 is expressed in rapidly proliferating cell types undergoing differentiation. In the mammary gland, Brca1 expression is induced during puberty, pregnancy, and following treatment of ovariectomized animals with 17 beta-estradiol and progesterone. These observations imply that Brca1 is involved in the processes of proliferation and differentiation in multiple tissues, notably in the mammary gland in response to ovarian hormones.

Animals↗

PubMed1989

5,6-Dichloro-1-beta-D-ribofuranosylbenzimidazole inhibits transcription elongation by RNA polymerase II in vitro.

The purine nucleoside analog 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) is a selective inhibitor of transcription by RNA polymerase II. Although a wealth of in vivo studies have suggested that DRB inhibits transcription by enhancing the premature termination of elongating polymerase molecules, in vitro studies to date have been interpreted to suggest that DRB acts at the level of transcription initiation. We have analyzed the mechanism of DRB-mediated transcription inhibition in vitro both in HeLa whole cell extracts and in a partially purified transcription system. The results indicate that the extent to which DRB inhibits the synthesis of a RNA transcript is directly proportional to its length. For example, DRB was found to preferentially inhibit transcription in vitro of promoter-distal relative to promoter-proximal portions of the adenovirus major late transcription unit. A factor potentially involved in mediating this inhibitory effect is identified. We conclude that the mechanism of DRB inhibition of transcription in vivo and in vitro are similar.

Dichlororibofuranosylbenzimidazole↗

PubMed1989

A yeast protein possesses the DNA-binding properties of the adenovirus major late transcription factor.

The adenovirus major late transcription factor (MLTF), or upstream stimulatory factor, is a human promoter-specific transcription factor which recognizes the near-palindromic sequence GGCCACGTGACC (R. W. Carthew, L. A. Chodosh, and P. A. Sharp, Cell 43:439-448, 1985; L. A. Chodosh, R. W. Carthew, and P. A. Sharp, Mol. Cell. Biol. 6:4723-4733, 1986; M. Sawadogo and R. G. Roeder, Cell 43:165-175, 1985). We describe here a protein found in the yeast Saccharomyces cerevisiae which possesses DNA-binding properties that are virtually identical to those of human MLTF. These two proteins recognize the same DNA-binding site, make the same purine nucleotide contacts, and are affected in the same manner by mutations in the MLTF-binding site.

Adenoviridae↗

PubMed1988

Human CCAAT-binding proteins have heterologous subunits.

We have characterized three distinct proteins present in HeLa cell extracts that specifically recognize different subsets of transcriptional elements containing the pentanucleotide sequence CCAAT. One of these CCAAT-binding proteins, CP1, binds with high affinity to CCAAT elements present in the human alpha-globin promoter and the adenovirus major late promoter (MLP). A second protein, CP2, binds with high affinity to a CCAAT element present in the rat gamma-fibrinogen promoter. Finally, the third CCAAT-binding protein is nuclear factor I (NF-I), a cellular DNA-binding protein that binds to the adenovirus origin of replication and is required for the initiation of adenoviral replication. CP1, CP2, and NF-I are distinct activities in that each binds to its own recognition site with an affinity that is at least three orders of magnitude higher than that with which it binds to the recognition sites of the other two proteins. Surprisingly, CP1, CP2, and NF-I each appear to recognize their binding site with highest affinity as a multisubunit complex composed of heterologous subunits. In the case of CP1, two different types of subunits form a stable complex in the absence of a DNA-binding site. Moreover, both subunits are present in the CP1-DNA complex. We thus propose the existence of a family of related multisubunit CCAAT-binding proteins that are composed of heterologous subunits.

Animals↗

PubMed1988

A yeast and a human CCAAT-binding protein have heterologous subunits that are functionally interchangeable.

The S. cerevisiae HAP2 and HAP3 gene products have been shown to recognize CCAAT-containing transcription elements as a HAP2/HAP3 multisubunit heterologous complex, or heteromer. Recently, we have demonstrated that the human sequence-specific DNA-binding protein, CP1, also recognizes CCAAT-containing transcription elements as a heteromer. Mammalian cells contain at least three distinct CCAAT-binding proteins, all of which appear to be multisubunit complexes composed of heterologous subunits. One of these proteins, CP1, has DNA-binding properties that are virtually identical to the yeast HAP2/HAP3 complex. These two proteins bind to the same target sequences, make the same DNA contacts, and are affected in a similar manner by mutations in the CCAAT element. Most surprisingly, the subunits of CP1 and HAP2/HAP3 are functionally interchangeable. That is, the yeast/human hybrid complexes that are formed retain the ability to specifically recognize CCAAT elements.

Biological Evolution↗

PubMed1988

Sp1, a CAAT-binding factor, and the adenovirus major late promoter transcription factor interact with functional regions of the gamma-fibrinogen promoter.

To study the factors which influence the coordinately and developmentally regulated expression of the three adjacent fibrinogen genes, we have defined the functional regions of the gamma-fibrinogen promoter and the proteins which bind to them. Using a series of 5' and internal deletion mutations, we found that sequences between 88 and 43 base pairs (bp) upstream of the gamma-fibrinogen transcription initiation site functioned in cis to direct properly initiated mRNA accumulation in transfected hepatocytes. The efficient function of these sequences was highly distance dependent, since transcriptional activity decreased by 92% when they were moved 32 bp upstream of the TATA box. We demonstrated that two known and one putative transcriptional factors interacted with this 47-bp sequence. The transcription factor Sp1 interacted with sequences between -51 and -46 as demonstrated by protection from DNase I digestion with the purified protein. Directly adjacent to the Sp1 site, between nucleotides -66 and -53, there was a sequence which bound a CAAT-binding factor. Finally, sequences just 5' to the CAAT factor-binding site interacted with the adenovirus major late transcriptional factor as previously demonstrated. Internal deletion mutations which disrupt these interactions diminished the activity of the promoter in vivo. One consequence of the interaction of these proteins is that a bend is placed in the DNA at or near their sites of interaction.

Base Sequence↗

PubMed1987

The adenovirus major late transcription factor activates the rat gamma-fibrinogen promoter.

The major late transcription factor (MLTF) is a 46-kilodalton polypeptide that specifically binds to and activates transcription from the major late promoter of adenovirus. The presence of this promoter-specific transcription factor in uninfected HeLa cell extracts suggests that MLTF is also involved in the transcription of cellular genes. This report demonstrates that MLTF specifically stimulates transcription of the rat gamma-fibrinogen gene through a high-affinity binding site. Stimulation of transcription by MLTF was not dependent on the exact position of the MLTF binding site with respect either to the transcription initiation site or to adjacent promoter elements. These results suggest that one of the cellular functions of MLTF is to control gamma-fibrinogen gene expression.

Adenoviruses, Human↗

PubMed1987

The major late transcription factor binds to and activates the mouse metallothionein I promoter.

Human (HeLa) cells contain a protein, MLTF, which specifically binds to a DNA sequence in the adenovirus 2 major late promoter and activates transcription of that promoter. The presence of MLTF in uninfected cells suggests that this factor contributes to the transcription of some cellular genes. We find that MLTF binds in a sequence-specific manner to the 5'-flanking region of the mouse metallothionein I (mMTI) gene. Binding was localized between -101 and -94 (relative to the initiation site at +1) by DNA-binding gel electrophoresis assay and DNA methylation interference analysis. As in adenovirus, binding occurred in a region containing the sequence CPuCGTGAC. Deletion of this sequence both eliminated the binding of MLTF and produced a fourfold reduction in transcriptional efficiency in vitro. In contrast to the intact promoter, transcription from the deletion mutant promoter was not stimulated by addition of purified MLTF to an in vitro reconstituted reaction. These results suggest that MLTF contributes to the transcription of cellular genes.

Adenoviruses, Human↗

PubMed1986

A single polypeptide possesses the binding and transcription activities of the adenovirus major late transcription factor.

A simple approach has been developed for the unambiguous identification and purification of sequence-specific DNA-binding proteins solely on the basis of their ability to bind selectively to their target sequences. Four independent methods were used to identify the promoter-specific RNA polymerase II transcription factor MLTF as a 46-kilodalton (kDa) polypeptide. First, a 46-kDa protein was specifically cross-linked by UV irradiation to a body-labeled DNA fragment containing the MLTF binding site. Second, MLTF sedimented through glycerol gradients at a rate corresponding to a protein of native molecular weight 45,000 to 50,000. Third, a 46-kDa protein was specifically retained on a biotin-streptavidin matrix only when the DNA fragment coupled to the matrix contained the MLTF binding site. Finally, proteins from the most highly purified fraction which were eluted and renatured from the 44- to 48-kDa region of a sodium dodecyl sulfate-polyacrylamide gel exhibited both binding and transcription-stimulatory activities. The DNA-binding activity was purified 100,000-fold by chromatography through three conventional columns plus a DNA affinity column. Purified MLTF was characterized with respect to the kinetic and thermodynamic properties of DNA binding. These parameters indicate a high degree of occupancy of MLTF binding sites in vivo.

Adenoviruses, Human↗

PubMed1985

An RNA polymerase II transcription factor binds to an upstream element in the adenovirus major late promoter.

A gel electrophoresis DNA binding assay has been used to identify proteins in HeLa cell extracts that specifically bind to the major late promoter of adenovirus. A major late promoter transcription factor MLTF has been detected as a discrete protein-DNA complex. MLTF binds specifically and with high affinity to sequences upstream of the TATA box of the major late promoter. This factor protects a 17 bp (-50 to -66) region in a DNAase I footprinting assay. The same region has been shown to be important for efficient transcription from the major late promoter both in vivo and in vitro. MLTF stimulates in vitro transcription only from a template containing this upstream region. The binding, footprinting, and transcription-stimulatory activities of MLTF cofractionate through two chromatographic steps. These results suggest that direct binding of MLTF to an upstream element activates transcription from the major late promoter.

Adenoviruses, Human↗

PubMed1982

DNA transfer of focus- and tumor-forming ability into nontumorigenic CHEF cells.

CHEF/18 fibroblastic cells derived from a Chinese hamster embryo are diploid and nontumorigenic and require multiple steps of chemical treatment and selection to produce tumorigenic derivatives. In this report, CHEF/18 cells and a mutant capable of growing in medium with a low concentration of serum, LS1-1, were recipients in DNA transfer experiments using the calcium phosphate coprecipitation method. Focus formation with donor DNAs from tumor-derived CHEF cells and from human bladder carcinoma cell line EJ gave yields of 0.02-0.59 focus per microgram of DNA per 10(6) recipients. In one experiment in which CHEF/18 cells were transfected with EJ DNA, the presence of human DNA was detected in five of seven foci by using a cloned Alu sequence. Cells from one of these foci gave rise to tumors in nude mice, and the DNA produced secondary CHEF/18 transfectants. Because normal human cells as well as CHEF/18 cells require multiple stages to become tumorigenic, these findings suggest that EJ cells contain tumor-inducing DNA as the result of prior changes that occurred during the development of this carcinoma.

Animals↗