Amplification and altered expression of the hsc70/U 14 snoRNA gene in a heat resistant Chinese hamster cell line

AUTOR(ES)

Chen, Ming-Shun

FONTE

Cell Stress Society International

RESUMO

We have recently demonstrated that the heat resistant phenotype of the HR-1 variant isolated from HA-1 Chinese hamster fibroblasts after a series of heat shocks is associated with the increased expression of Hsc70, the constitutive form of Hsp70 (Laszlo and Li 1985). Here, we report the cloning and characterization of the Chinese hamster hsc70 gene and its organization and expression in wild type HA-1 and permanently heat resistant HR-1 cells. DNA sequencine revealed that the structure and nucleotide sequence of the hamster hsc70 gene in highly homologous to the human and rat genes coding for Hsc70. Three of the eight introns of the hamster hsc70 gene encode U14 small nucleolar RNAs, as has been demonstrated in other species.Although putative transcriptional elements, including a TATA box, two inverted CAT boxes, and two sets of heat shock elements (HSEs) are completely conserved in the human and hamster hsc70 genes, the regulation of expression of the hamster hsc70 gene in different from that reported for its human counterpart in the mRNA coding for Hsc 70 increases at least 10-fold after a mild heat shock in Chinese hamster cells while no induction of Hsc70 by heat shock has been reported in human cell lines. In situ hybridization revealed a complex chromosomal rearrangement in HR-1 cells which results in the 4- to 5-fold amplification of the hsc70 gene as indicated by genomic Southern blots. In association with this amplification of the hsc70 gene, the levels of Hsc70 mRNA and U14 snoRNA are increased in the HR-1 cells under both normal growing conditions and after heat shock. Thus, the elevated expression of both Hsc70 and U14 snoRNA might play a role in the heat resistant phenotype of the HR-1 cells. This is the first report of the amplification of a heat shock gene and the possible induction of gene amplification by heat shock.

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