Characterization of the non-histone nuclear proteins associated with rapidly labeled heterogeneous nuclear RNA.
Year: 1977
Type: article
Abstract: Heterogeneous nuclear RNA (HnRNA) is associated with a set of specialized RNA-binding proteins. Mild ribonuclease digestion of intact HnRNA-protein complexes released 15 S ribonucleoprotein (RNP) particles containing poly(A) and its associated protein and 40 S RNP particles containing most of the HnRNA sequences. Highly purified 40 S RNP particles have been obtained from rat liver by centrifugation of nuclear extracts on sucrose density gradients and isopycnic banding on Metrizamide density gradients. These RNP preparations contain 27% of the total HnRNA sequences of rat liver, and appear homogeneous when viewed in negative contrast in the electron microscope and by centrifugation studies using velocity sedimentation in sucrose density gradients or isopyenic banding in density gradients of cesium salts. Analysis of the proteins in the rat liver 40 S RNP particles by two-dimensional gel electrophoresis demonstrated that the 40 S RNP particle is composed of 12 major protein components with molecular weights ranging from 29,000 to 42,000 which accounted for 75% of the total protein mass and 13 minor protein components with molecular weights greater than 42,000. The proteins in the 29,000 to 42,000 group were fractionated by ion exchange chromatography. The amino acid compositions of the purified protein fractions were strikingly similar and shared several unusual features that distinguish these HnRNA-associated proteins, as a group, from the histones and the non-hi&one chromosomal proteins. Each of the RNP proteins have basic charge characteristics (p1 greater than 8.0) high glycine (25 mol %), low cysteine, and little detectable methionine. Like the histones, the HnRNP proteins are subject to extensive postsynthetic modification. We have identified the unusual amino acid NC, NC (CH,),-L-arginine in acid hydrolysates of some of the RNP proteins and shown that this amino acid
Source: Journal of Biological Chemistry
Authors: J Karn, G Vidali, L C Boffa, V G Allfrey
Institutions: MRC Laboratory of Molecular Biology, Rockefeller University
Language: English
Topic: RNA Research and Splicing
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W159115069