Sequence preference of mouse H1(0) and H1t

Histone H1 proteins bind to DNA and are important in formation and maintena nce of chromatin structure. Little is known about differences among variant H1 histones in their interactions with DNA. We examined the effects of his tones H1(0) and H1t on thermal denaturation of several DNA species. One of the DNA molecules was a 214-base-pair fragment from the plasmid pBR322, whi ch contains an AT-rich and a GC-rich region. Both H1(0) and H1t bound prefe rentially to one region of the DNA fragment, a region that is relatively GC -rich. This result indicates that histones H1(0) and H1t are not totally no nspecific but rather bind with some sequence preference to DNA. This conclu sion was supported by studies of other DNA species, including two 92-base-p air fragments derived from the two regions of the 214-mer, and several synt hetic homocopolymers of DNA. Data obtained with the homocopolymers suggeste d that the binding preference was not simple preference for GC base pairs. The binding of the two H1 variants was not identical: there appear to be di fferences in binding site sizes, affinities, and sequence selectivities bet ween H1t and H1(0).