Isolation of Chicken hsp90β Gene Promoter

In order to define the mechanisms responsible for the differential expression of chicken hsp90α and β genes, a portion of the chicken hsp90β genomic sequence, including 3081 bp upstream from the transcription initiation site and 2718 bp of structural gene sequence which covers 7 exons and 6 introns was investigated. The transcriptional initiation site was determined by primer extension, RNAase and S1 nuclease mapping, Northern blot and cloning of 5′ end of cDNA. The first intron, as in other hsp90 genes, is located just before the ATG initiation codon. Three Sp l sites are located near the TATA box. The apparent major divergence with the hsp90α promoter is that, in the hsp90β promoter, the only CAAT box and HSE element are located at about 3 and 2 kb upstream the TATA box,respectively. These features may explain why chicken hsp90β mRNA is generally less abundant than α and is not inducible by heat shock or serum/growth factor stimulation.