PubMed Health⌕ Search

Biomedical subjects

J Sarid

Publications and source records attributed to J Sarid.

7 recordsLinked to original sources
PubMed1994

Glial fibrillary acidic protein transcriptional regulation is independent of a TFIID-binding downstream initiator sequence.

Previous studies have shown that the promoter of the glial fibrillary acidic protein (GFAP) gene contains a transcriptional initiator located downstream from the transcription initiation (cap) site. This initiator was shown to be essential for efficient in vitro TATA box binding and function of TATA box-binding factor (TFIID); its deletion significantly reduced in vitro template transcription by the GFAP promoter and inhibited almost completely expression of a reporter gene under control of human GFAP promoter and upstream sequences in glial cells. However, although activity of initiator-containing GFAP promoter in human and murine GFAP-reporter constructs in transfected cells was shown to increase sharply when upstream cis-acting elements are added, initiator-lacking murine constructs have shown a small GFAP promoter region to have high activity in glioma cells, with no increase in activity when regulatory sequences are extended further upstream. These findings suggested a possible difference between the in vitro and in vivo effects of the downstream initiator on the promoter region itself, as well as an in vivo interplay between the initiator and regulatory sequences upstream from the promoter region. Here we have analyzed the effect of the downstream initiator on gene expression in cells using matched (pairs of otherwise identical initiator-containing and initiator-deleted plasmids) constructs extending to different upstream positions. We show that matched initiator-containing and initiator-deleted counterparts direct similar expression levels, and that, with or without the downstream initiator, expression levels increase sharply when upstream sequences are added to the GFAP promoter. Our results show that the downstream initiator is not required for GFAP transcriptional activity in cultured cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Overexpression of oncogene products can cause tumor progression without parenchymal infiltration in the rat brain.

Tumor cell progression and parenchymal infiltration play important roles in the pathogenesis of gliomas. Using retrovirally marked rat 9L gliosarcoma cells, which when injected in the CDF rat brain form noninfiltrating tumors which grow only surrounding existing blood vessels, we were able to investigate elements of tumor growth and progression within the substance of the brain. Transfection of 9L by oncogenes associated with tumor progression and expressed in gliomas resulted in alterations in the in vivo phenotype of these cells, with the production of faster growing, well-vascularized, large solid tumors. However, diffuse infiltration was not seen. Moreover, coinjection of 9L or its transfectants together with the infiltrative C6 cell line resulted in a mixed tumor of noninfiltrating 9L cells in an environment of infiltrating C6 cells, suggesting that the infiltrative ability of C6 cells is controlled on the individual cell level.

Animals↗
PubMed1991

Identification of a cis-acting positive regulatory element of the glial fibrillary acidic protein gene.

Developmental regulation of astrocyte-specific expression of the glial fibrillary acidic protein (GFAP) gene reflects transition of immature glioblasts to mature astrocytes. Described here is the cloning and sequencing of the 5'-flanking region of the mouse GFAP gene. It contains a glial-specific positive cis-acting regulatory element that directs preferential expression of a linked reporter gene when transfected into GFAP-positive glioblastoma cells. Sequence analysis of this region revealed the presence of a putative AP-1 binding site, implying a possible role for AP-1 factors in the astroglial-specific expression of the GFAP gene.

Astrocytes↗
PubMed1989

The mast cell-specific expression of a protease gene, RMCP II, is regulated by an enhancer element that binds specifically to mast cell trans-acting factors.

The rat mast cell protease gene, RMCP II, is specifically expressed in the mucosal subclass of rat mast cells. We show here that the 5'-flanking region of this gene contains a mast cell-specific enhancer that directs preferential expression of a linked reporter gene (human growth hormone) transfected into rat basophilic leukemia cells. A DNA fragment containing the enhancer sequence is capable of binding specifically to mast cell nuclear trans-acting factors. The sequence of this enhancer element contains a region of homology to a consensus core sequence present in the enhancer region of the pancreatic protease genes.

Animals↗
PubMed1987

Evolutionarily conserved regions of the human c-myc protein can be uncoupled from transforming activity.

The myc family of oncogenes contains coding sequences that have been preserved in different species for over 400 million years. This conservation (which implies functional selection) is broadly represented throughout the C-terminal portion of the human c-myc protein but is largely restricted to three clusters of amino acid sequences in the N-terminal region. We have examined the role that the latter three regions of the c-myc protein might play in the transforming function of the c-myc gene. Several mutations, deletions and frameshifts, were introduced into the c-myc gene, and these mutant genes were tested for their ability to collaborate with the EJ-ras oncogene to transform rat embryo fibroblasts. Complete elimination of the first two N-terminal conserved segments abolished transforming activity. In contrast, genes altered in a portion of the second or the entire third conserved segment retained their transforming activity. Thus, the latter two segments are not required for the transformation process, suggesting that they serve another function related only to the normal expression of the c-myc gene.

Animals↗
PubMed1986

A translocated human c-myc oncogene is altered in a conserved coding sequence.

We have cloned and characterized a c-myc (now designated MYC) oncogene that had been translocated into the mu switch region of the immunoglobulin heavy chain locus in a Burkitt lymphoma cell line. The breakpoint of the translocation occurs within the first intron of the c-myc gene, thereby separating the untranslocated first exon from the two coding exons. Transcription from the translocated gene arises from a cryptic promoter within the first intron, which produces a 438-nucleotide untranslated 5' region. The amino acid sequence of the protein encoded by the c-myc gene has been substantially altered. In particular, a compensating set of frameshift mutations alters a string of 24 amino acids in a region of the protein tightly conserved in human, mouse, and chicken c-myc genes as well as in the human N-myc and L-myc oncogenes. Despite this, the mutated gene retains a reduced transforming ability in a rat embryo fibroblast focus-formation assay.

Amino Acid Sequence↗