Selective distribution of histone H1 variants and high mobility group proteins in chromosomes

Recent results on the differential distribution of sequence variants of histone H1, of proteins of the HMG 1/2 family, and of HMGI in polytene chromosomes are reviewed. Several organisms are known to contain two different HMG 1/2 proteins. InChironomus, one of them is restricted to decondensed puffs and may have a specific function. One of the H1 variants ofChironomusis found only in a minority of chromosome bands and differs from the other H1 proteins of the organism by genomic organization and by an inserted structural motif that is also present in single H1 variants of other organisms.