Involvement of Nonhistone Chromosomal Proteins in Transcriptional Activity of Chromatin during Wheat Germination

Abstract

To clarify how the transcriptionally inactive chromatin of dormant wheat seed embryos becomes active during germination, we studied two kinds of chromatin-associated proteins: histones and nonhistone proteins found in wheat germ.Two major nonhistone proteins were solubilized from purified germ chromatin with 5 molar urea, and were separated from histones and chromosomal RNA by BioRex-70 resin and diethylaminoethyl-cellulose chromatography, respectively. We found that purified 5 molar urea-soluble nonhistone proteins, including the two major nonhistone proteins, had no effect on the transcription of native wheat DNA.Two kinds of chromatins were reconstituted by gradient dialysis from a mixture of DNA, germ histones, and nonhistone proteins derived from germs or germinated seedlings. Reconstituted chromatins had a 1.4- to 1.6-fold higher protein content than DNA content, protein components similar to native chromatin, and had only about 17 to 25% and 37% the transcriptional activities of native seedling and germ chromatins, respectively. Using the transcriptional activity of chromatin reconstituted from DNA and histones alone as a standard, one kind of reconstituted chromatin containing nonhistone proteins of germ was only about one-fourth as active as the standard. Another with nonhistone proteins from seedlings was about 1.3 to 1.5 times more active than the standard.The ratio of histones to DNA content is approximately 1.3 during germination, but the proportion of histone H1 to the total histones is reduced.