Poly(riboadenylate)-containing messenger ribonucleoprotein particles of chick embryonic muscles

Abstract

Poly(A)-containing cytoplasmic messenger ribonucleoprotein (mRNP) particles were isolated from subcellular fractions of 12-1 4-day-old chick embryonic muscles by chromatography on oligo(dT)-cellulose and elution of the bound m R N P with 50% formamide. Two types of mRNP, free or nonpolysomal and polysome-derived, were obtained from the postpolysomal supernatant fraction and EDTAdissociated polysomes, respectively. The m R N P were characterized by the absence of ribosomal RNAs and typical ribosomal proteins, by the presence of a limited number of characteristic proteins, and by the polydisperse sedimentation of the particles and their R N A moieties in sucrose gradients. Although the two types of particles show many similarities, their buoyant densities and NaDodS0,-gel electrophoretograms of their protein moieties indicate that they represent two distinct types of macromolecular complexes. The free m R N P are relatively protein rich and contain 10 distinct proteins in the 40 000-100 000 molecular weight range. The polysome-derived m R N P are comparatively protein deficient I n eukaryotic cells mRNAs are complexed with proteins to form messenger ribonucleoprotein (mRNP)' particles (Perry Greenberg, 1975). Two types of m R N P particles, polysome-derived mRNP, which are released by the dissociation of polyribosomes, and nonpolysomal free mRNP (also referred to as informosomes), have been reported in the literature. The polysomal m R N P particles derived from a large number of species and tissues contain two major proteins of about 52 000 and 78 000 molecular weight and a large number of additional

Cytoplasmic utilization of liposome-encapsulated myosin heavy chain messenger ribonucleoprotein particles. During muscle cell differentiation.

“…3). These are similar to those reported by Jain and Sarkar (32). It cannot be determined at this time ifall ofthese proteins are truly associated with the mRNPs in vivo.…”

Specific mRNP complexes

“…I n vivo ultraviolet cross-linking has recently allowed detection of proteins which interact closely with RNA in the cytoplasm of other eukaryotic cells [39-421. A comparison of the global population of polysomal and free mRNP fractions reveals a wide spectrum of polypeptides some of which are similar in terms of molecular mass. Furthermore the free mRNP complexes are more protein-rich than those isolated from polysomes, an observation noted by other investigators not employing the ultraviolet cross-linking procedure [l, 4, 10, [43][44][45]. An examination of histone H4 mRNPs from these two fractions reveals that the polypeptides associated with the histone H4 mRNAs represent a subset of those proteins found in the mRNPs from either fraction.…”

Association of cap binding protein‐related polypeptides with cytoplasmic RNP particles of chick embryonic muscle

“…These results suggest that the CBP-related protein (Mr 78000) identified in free mRNP and the 10 S iRNP is distinct from the poly(A)-bound protein (MI 78000), which is present in polysomal mRNP particles of a wide variety of eukaryotic cells [9, 17, by our observation that the lo-12 S poly(A)-protein segment isolated from polysomal mRNP [8] and containing the poly(A)-bound M, 78000 protein [8] did not give any immunostaining with anti-CBP antibody (not shown).…”

“…In agreement with [12,13,15,16], a complex set of proteins (Mr 15 000-150 000) is present in both 20-40 S free mRNP particles (A, gel 1) and the 10 S iRNP particles (B, gel 1). The polysomal mRNP particles (C, gel l), with a relatively simple protein pattern (A,& 35000-78000) [8,18] gave no detectable immunostaining after reaction with anti-CBP antibody (C, gel 2). Various preparations of polysomal mRNP isolated by different techniques such as oligo(dT)-cellulose chromatography of EDTA-dissociated polysomes and differential elution of the bound mRNP particles at 25°C and 45°C to yield subpopulations of polysomal mRNP, as in [22] were also tested in order to confirm the absence of CBP-related polypeptides in these particles.…”

“…The isolation and characterization of various classes of cytoplasmic RNP particles from chick embryonic muscle have been reported in [ 12-141. These include a novel class of translation inhibitory 10 S RNP (iRNP) containing a 4 S RNA (iRNA) ; the 20-40 S free mRNP particles [15,16]; and the polysomal mRNP [8,17,18]. Using a monoclonal antibody to purified CBP isolated from rabbit reticulocytes [7], we report here that there is specific association of CBP-related polypeptides in certain types of RNP particles.…”