Sp1-mediated transcription regulation of TAF-Ialpha gene encoding a histone chaperone

TAF-I, one of histone chaperones, consists of two subtypes, TAF-Iα and TAF-Iβ. The histone chaperone activity of TAF-I is regulated by dimer patterns of these subtypes. TAF-Iβ is expressed ubiquitously, while the expression level of TAF-Iα with less activity than TAF-Iβ differs among cell types. It is, therefore, assumed that the expression level of TAF-Iα in a cell is important for the TAF-I activity level. Here, we found that TAF-Iα and TAF-Iβ genes are under the control of distinct promoters. Reporter assays and gel shift assays demonstrated that Sp1 binds to three regions in the TAF-Iα promoter and two or all mutaions of the three Sp1 binding regions reduced the TAF-Iα promoter activity. ChIP assays demonstrated that Sp1 binds to the TAF-Iα promoter in vivo. Furthermore, the expression level of TAF-Iα mRNA was reduced by knockdown of Sp1 using siRNA method. These studies indicated that the TAF-Iα promoter is under the control of Sp1.