MOLECULAR AND CELLULAR CHARACTERIZATION OF CRP1, A DROSOPHILA CHROMATIN DECONDENSATION PROTEIN

CRP1, a Drosophila nuclear protein that can catalyze decondensation of demembranated Xenopus sperm chromatin was cloned and its primary stru cture was deduced from cDNA sequence, Alignment of deduced amino acid sequence with published sequences of other proteins revealed strong ho mologies to Xenopus nucleoplasmin and NO38, CRP1 is encoded by one or several closely related genes found at a single locus, position 99A on the right arm of chromosome 3, CRP1 mRNA is expressed throughout Dros ophila development; it is highest during oogenesis and early embryogen esis. mRNA levels correlate closely with levels of protein expression measured previously, Results of chemical crosslinking indicate that CR P1 is either tetrameric off pentameric; similar ambiguity was revealed by direct visualization using scanning transmission electron microsco py. Consistent with previously published results, parallel crosslinkin g studies of Xenopus nucleoplasmin suggested a pentameric structure. S canning transmission electron microscopic examination after negative s taining revealed that CRP1 and Xenopus nucleoplasmin are morphological ly similar. CRP1 is able to substitute for nucleoplasmin in Xenopus eg g extract-mediated sperm chromatin decondensation. In vitro, CRP1-indu ced decondensation is accompanied by direct binding of CRP1 to chromat in. (C) 1997 Academic Press.