title: DNAase hydrolysis of chromatin DNA in intact sea urchin sperm cells. Effect of the ionic strength on the digestion parameters.
abstract: Chromatin DNA in intact functional Sphaerechinus granularis sperm cells has been digested with micrococcal nuclease at three different ionic strength conditions. The results show a highly-flexible chromatin organization similar to that found in sperm heads. The rate of digestion, the limit value of acid-soluble material and the fragmentation pattern show that the sensitivity of nucleosome and internucleosome DNA regions to nuclease hydrolysis depends on a delicate balance of polar and non polar interactions. At low ionic strength, both nucleosome and internucleosome regions are rapidly and completely hydrolysed at the same time and a transient subunit fragment of 120 b.p. average length is formed. At high ionic strength, internucleosome regions are preferentially hydrolysed; there is a limit digest value and a stable subunit fragment of 140 b.p. average length is formed. A supernucleosome organization in the high ionic strength environment of the sperm cells is suggested by the transient preferential formation of heptamers of nucleosome DNA fragments.
mesh_terms: D000818:Animals; D002843:Chromatin; D004247:DNA; D004262:DNA Restriction Enzymes / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009994:Osmolar Concentration; D012617:Sea Urchins; D013094:Spermatozoa / Q000032:analysis*
chemical_list: D002843:Chromatin; D004247:DNA; D003851:Deoxyribonucleases; D004262:DNA Restriction Enzymes