The RNA Fractions of Chromatin from L-Cells

Abstract
Chromatin obtained from L-cell nuclei has been shown to contain three distinct RNA fractions. One, a low molecular weight RNA fraction (3–7 S), has been isolated and purified. Two-dimensional polyacrylamide gel electrophoresis indicates that this fraction contains at least 28 diverse RNA components. Both the rate of incorporation of [32P]H3PO4 into this fraction and the loss of [3H]uridine from the fraction after a 1 h pulse suggest that these RNA's are slowly synthesized and are very stable. Not all the species within the low molecular weight fraction have the same turnover rates.A high molecular weight RNA fraction (15–30 S) has also been isolated from L-cell chromatin. From the rate of [32P]H3PO4 incorporation and the loss of [3H]uridine from this fraction after a 1 h pulse, it appears that this RNA fraction is rapidly synthesized and is either unstable or is rapidly removed from chromatin once synthesized.A third RNA fraction also present in L-cell chromatin appears to be tightly bound to the DNA. It has been isolated and shown to be of low molecular weight (3–5 S). This RNA also appears to be rapidly synthesized and to be metabolically unstable.