| Summary: | 碩士 === 國防醫學院 === 生物及解剖學研究所 === 96 === The p53 family comprises three members: p53, p63, and p73.Whereas p53 plays a role in tumor suppression,p63 and p73 mainly involve in the developmental and differentional programs. p53 trans-activates downstream genes by binding to a whole site of p53 binding site which consists of direct repeats of the half site PuPuPuC(T/A)(T/A) GPyPyPy. p53 also can bind to a half site of p53 binding site but without transcriptional activity. In our previous study, TAp63α, can activate keratin 14 through a half-site of p53 binding site (-140~-131) on keratin 14 promoter. In contrast, oligo-promoter of this p53 half site couldn’t be activated by TAp63α. Therefore, other co-factors might participate in the p63 activation of K14 promoter through a p53 half site. According to a serial deletion mutants of K14 promoter for reporter assay, a candidate of co-factor binding sequence was found at the -269~-160 of K14 promoter. Using sequence homologous searching, a HMG box binding protein sequence was found at -168~-161 of the K14 promoter. Three HMG box binding proteins HMGB1, HMGB2 and SSRP1 were reported to be the co-activator of p63. According to our RT-PCR results, these binding proteins can be detected in H1299 cell line (a p53 null cell). We have cloned SSRP1 and HMGB2 gene and then co-expressed these clone with p63 in H1299 cell line .We used DAPA to confirm SSRP1 could bind to HMG binding site in K14 promoter. Using semi-quantitave PCR, we found SSRP1 and p63 could enhance K14 promoter activity much more than p63 alone. Therefore, we believed that SSRP1 is the possible co-factor for p63 to activate K14 promoter.
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