Is Histone H1 a CaMBP?
The isolation of Dictyostelium histone H1 (DdH1) as a potential CaMBP was especially intriguing not only for its link to chromosome condensation and gene regulation but also as a potential cell cycle component regulated by calmodulin. Histone H1 belongs to the linker histone family that binds both the linker DNA between nucleosomes and adjacent nucleosomes in nuclear chromatin and, as a result, has been suggested to regulate gene activity. In addition to roles in chromatin structure and gene regulation, recent research has shown that H1 also plays roles in DNA repair and synthesis and can bind to various other proteins. The inter-relationship between H1 and CaM and the actual binding of the nucleoprotein to CaM has been suggested by previous work but never proven. Binding analyses with CaM-agarose revealed that DdH1 bound in both the presence of either Ca2+ or EGTA. Initial scans of the DdH1 sequence in the Calmodulin Target Database and by visual analyses revealed the presence of two
