Attachment of mRNA to the cytoskeletal framework and translational control of gene expression in rat L6 muscle cells

Author:

Bag Jnanankur,Pramanik Saroj

Abstract

The mRNA of rat L6 muscle cells was distributed between a detergent-insoluble fraction containing the cytoskeletal framework and a detergent-soluble fraction. The majority of cytoskeleton-bound mRNA was translationally active and present as polysomes. The mRNA of the detergent-soluble fraction was not associated with the ribosomes and, thus, considered to be the repressed free population. The binding of mRNA was not mediated through ribosomes or the poly(A) region of mRNA. Cross-linking of RNA and proteins was used to examine whether proteins of the cytoskeletal framework were involved in binding mRNA to this structure. Analysis of the mRNA–protein complexes has shown that a large number of polypeptides of molecular masses between 15 and 220 kilodaltons (kDa) were associated with both cytoskeleton-bound and soluble mRNAs. However, a 165-kDa polypeptide was preferentially associated with cytoskeleton-bound mRNA–protein complexes. This polypeptide was also enriched in the total proteins of the cytoskeleton fraction. We have suggested a receptor-like role for the 165-kDa polypeptide in binding mRNA to the cytoskeletal framework. The mechanism of interaction between the cytoskeleton and mRNA was further examined by using a ghost-monolayer transcription system. The mRNA synthesized by this transcription system was preferentially retained in the detergent-insoluble cytoskeleton component of the ghost-monolayer preparation. To understand the physiological significance of the distribution of mRNA between the translationally active cytoskeleton-bound and repressed soluble fractions we have isolated a cDNA clone for a 1.3-kilobase (kb) mRNA. This mRNA was preferentially repressed in myotubes. Distribution of this mRNA was determined by Northern blot analysis using the recombinant plasmid. This analysis indicates that nearly 90% of this mRNA was not associated with ribosomes. In contrast, only 3% of α-actin mRNA was found in the repressed population. However, approximately 25% of the 1.3-kb mRNA was present as repressed free messenger ribonucleoprotein. This behaviour is again different from that of actin. All of the cytoskeleton-bound α-actin mRNA was associated with polysomes. Furthermore, most of the small amount of α-actin mRNA which was present in the soluble fraction was also associated with polysomes. We have, therefore, concluded from these observations that binding of mRNA to the cytoskeleton framework and translation of mRNA are two separate events. We have suggested that mRNA is transported to the cytoplasm as a cytoskeleton-associated complex and further interaction with ribosomes may stabilize this complex. Translationally repressed mRNA which fails to bind to ribosomes may, therefore, be preferentially released from the cytoskeleton framework.

Publisher

Canadian Science Publishing

Subject

Cell Biology,Molecular Biology,Biochemistry

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3