Regulation of human hsp90α gene expression

Abstract

Mammalian HSP90K K and HSP90L L are encoded by two individual genes. On the basis of the upstream sequences of the human hsp90K K gene, GenBank accession number U25822, we have constructed CAT reporter plasmids driven by individual fragments of the hsp90K K gene. We found that (1) the proximal heat shock element complex located at 396/360 enhances hsp90K K promoter expression; (2) heat shock induction depends upon the coexistence of distal heat shock element at 31031/ 31022 and the proximal heat shock element complex of the hsp90K K gene; (3) unlike hsp90L L, downstream sequences of the transcription start site inhibit hsp90K K expression. We conclude that the regulatory mechanisms for the expression of hsp90K K and hsp90L L genes are different.z 1999 Federation of European Biochemical Societies.

PKCϵ Is a Unique Regulator for hsp90β Gene in Heat Shock Response

“…Despite the fact that Hsp90␣ and Hsp90␤ are highly homologous at the protein level, we have demonstrated earlier that the regulatory sequences and mechanisms that control the expression of these two genes are completely different (13,14). Studies from others and ours suggest that distinct signaling mechanisms are involved in the precise regulation of each hsp90 gene in a heat shock response.…”

“…For quantifying the promoter activity of human hsp90 genes, the Ϫ1756/ϩ37 fragment of the hsp90␣ gene and the Ϫ1039/ϩ1531 fragment of the hsp90␤ gene were independently fused to the upstream of a CAT reporter gene in pBLCAT3 to form reporter plasmids of p90␣ 1 -CAT and p90␤ 3.1 -CAT, respectively (13,14). A transfection control plasmid was constructed in which the ϩ698/ϩ1003-bp fragment of the CAT gene was deleted to express a mutant CAT and was designated as pM-CAT (28).…”

“…There are two cytoplasmic versions of the Hsp90 subfamily in mammalian cells encoded by two distinct genes, the hsp90␣ and hsp90␤ (11,12). Although Hsp90␣ and Hsp90␤ proteins share very high homology, we have demonstrated that the regulation mechanisms of the two genes are quite different (13,14): hsp90␣ is more sensitive to heat shock induction, whereas the hsp90␤ gene is the major cellular counterpart responding to mitogenic stimulation (15). We reported elsewhere (16) that Hsp90 is not only induced in stress response but also uniquely expressed in mitogen-activated T lymphoid cells, indicating its potential importance in cell growth.…”

Direct Activation of HSP90A Transcription by c-Myc Contributes to c-Myc-induced Transformation

“…Cloning of the Human HSP90A Promoter Region and Generation of HSP90A Promoter-driven Reporter Constructs, Transient Transfection, and Luciferase Assays-The genomic region flanking the HSP90A gene promoter was cloned by PCR amplification of human genomic DNA to generate a genomic fragment according to the published sequence (48,49), which contains 1430 bp 5Ј upstream of the HSP90A transcription start site, and the sequence was verified by sequencing. HindIII and BamHI sites were created to facilitate cloning.…”

“…An E-box site (CACGTG) is located in the proximal promoter. We analyzed whether the c-Myc/MAX binding site could mediate transcriptional activation of the HSP90A by c-Myc by studying whether c-Myc could activate the transcription of a reporter gene linked to HSP90A promoter sequences (48,49). To this end, we constructed a reporter vector (HSPLuc1430; see Fig.…”