Heterogeneity of chromosomal RNA

Chromosomal RNA: Its Properties

“…Artman and Roth define cRNA as "the RNA associated with the proteins which float in 4M CsCI" (5). A similar definition of cRNA is used operationally by Szeszaik and Pihl (6). The RNA that associates with the CsCl skin is more properly termed "skin RNA," and includes, in addition to cRNA as defined earlier in this report, a heterogeneous collection of RNA molecules that are adventitiously trapped by the proteins that float to the surface of CsCl (5).…”

“…This result suggests that cRNA is not a random mixture of RNA fragments, although the possibility that this merely reflects the specificity of nucleases cannot be excluded. 6) Additional evidence that ascites cRNA is a distinctive RNA class is derived from in vivo half-life studies (JO). The decay kinetics of pulse-labeled cRNA follow a linear first-order profile; this suggests that cRNA is a single kinetic component (10).…”

Nature and origins of chromatin-associated ribonucleic acid of avian reticulocytes

“…Nature of cRNA Isolated by a Sodium Deoxycholate Procedure. The CsCl procedure for cRNA isolation can yield artefactually produced RNA fragments (Artman and Roth, 1971;Szeszak and Pihl, 1972;this work). Holmes et al (1972) suggest that other cRNA isolation methods may overcome difficulties associated with the CsCl procedure.…”

Polynucleotides associated with histone preparations

“…The general conclusion is that all histone fractions prepared by acid extraction and by salt dissociation are contaminated to varying degrees by heterogeneous polynucleotides. This conclusion and those ofHeyden & Zachau (1971), Artman & Roth (1971), Hill et al (1971 and Szeszak & Pihl (1972) must challenge the significance of the so-called 'unique' histone-bound RNA species and their relevance to specific repression mechanisms. The results, together with the analyses of extracts from 32P-labelled cell nuclei of the Chinese hamster ovary, published by Shepherd et al (1970), are also relevant to metabolic studies of histone phosphorylation.…”

“…Heyden & Zachau (1971) have since described experiments showing that the RNA bound to nuclear proteins from calf thymus glands was, for the most part, derived from tRNA. It has been shown also by Artman & Roth (1971), Hill et al (1971) and Szeszak & Pihl (1972) that RNA associated with the chromosomal proteins of various chicken tissues, sea urchin embryos and rat liver comprises more than one type of RNA, the majority of which is not covalently attached to protein. In the present paper we describe some studies on the properties of nucleotides associated with various histone preparations.…”