Studies on deoxyribonucleoproteins. IX. Subfractions of deoxyribonucleoproteins from rat and mouse liver.

By carrier-free continuous electrophoresis, deoxyribonucleoprotein from rat and mouse liver could be separated into two subfractions. The more anodic fraction (DNP I), comprising 5 - 8 per cent of the total, contains fewer proteins (two types of histones only). [3H]Cyclophosphamide caused in vivo a 2.5 times higher alkylation of the DNA in in DNP I than of the DNA in DNP II. These and additional results led to the suggestion of a structural model with DNP I as a spacer in the deoxyribonucleoprotein fiber.