Regulation of troponin C synthesis in chicken cardiac muscle cell cultures

Malhotra, Suman Bala (1986) Regulation of troponin C synthesis in chicken cardiac muscle cell cultures. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (30MB)

Abstract

Most of the contractile muscle protein genes have been extensively examined to understand the mechanisms controlling tissue-specific gene expression in skeletal muscle. However, very little is known at the molecular level about another major contractile muscle protein, troponin C. Furthermore, very little is known about the regulation of gene expression in cardiac muscle. In this study, slow troponin C has been examined to understand its differentiation and regulation in chicken cardiac myocytes. -- Dot blot hybridisation and restriction endonuclease analysis indicated that the chicken slow troponin C gene was present as a single copy. Although, troponio C is a very conserved protein, the conservation at the DNA level is not known. When DNA from various species was compared by Southern blot hybridisation with a quail troponin C cDNA probe, I found that quail troponin C DNA was non-homologous to DNA from other classes. -- The regulation of troponin C protein synthesis in cardiac myocyte cell cultures was examined in this study. Cultured myocyte cells were pulse-labelled with ³⁵S-methionine, at different days after plating, and the protein synthesis levels were compared by two-dimensional gel electrophoresis. At the same time, total cellular RNA was extracted and troponin C mRNA levels were examined by Northern blot analysis, using a quail troponin C cDNA probe. The results showed that mRNA accumulation closely paralleled the synthesis of troponin C, suggesting its principal mode of regulation to be transcriptional. However, the decrease in the level of troponin C polypeptide synthesis was somewhat greater than the observed decrease in the mRNA level, suggesting a possible translational control of gene expression. Furthermore, when troponin C protein synthesis levels, at different days of plating, were compared with those of actin and tropomyosin, the results indicated that unlike skeletal contractile muscle proteins, these cardiac contractile muscle proteins were not co-regulated. -- The possible association of the transcriptionally active troponin C gene of cardiac myocytes with a nuclear sub-structure called nuclear matrix was also examined. Results indicated that the transcriptionally active troponin C gene was not preferrentially enriched in the nuclear matrix fraction.

Actions (login required)

View Item