Rajamanickam C, Selvamurugan N, Arun S, Siddiqui M A
Department of Biochemistry, School of Biological Sciences, Madurai Kamaraj University, India.
Cell Mol Biol. 1992 Feb;38(1):81-9.
In vitro translation of RNA transported from the rat heart nuclei has suggested that the transport of translatable messages from hypertrophic heart nuclei is greater than from sham-operated heart nuclei. An increased translation activity was observed in cell-free system with RNA transported from sham-operated heart nuclei in presence of hypertrophic heart cytosol, than from sham-operated heart cytosol. Similar results were obtained when myosin heavy chain (MHC) mRNA in the transported RNA was analyzed by slot-blot hybridization using beta cDNA probe. Immunoprecipitation analysis of the translated products using beta MHC isozyme specific antibody indicated that the increased levels of beta MHC specific mRNA in the RNA transported from sham-operated heart nuclei in presence of hypertrophic heart cytosol than sham-operated heart cytosol. Direct quantitation of alpha and beta MHC messengers by slot-blot hybridization analysis of transported RNA using oligomeric probes corresponding to the 3' untranslated regions of alpha and beta MHC mRNAs revealed that an increased transport of both alpha and beta MHC specific mRNAs from sham-operated heart nuclei in the presence of hypertrophic heart cytosol occurs, of which beta MHC mRNA is more than that of alpha MHC. In contrast, slot-blot hybridization analysis of the radioactive RNA synthesized during transcription in vitro in nuclei obtained from sham-operated as well as hypertrophic hearts has shown an increased synthesis of alpha in sham nuclei and that of beta in hypertrophic heart nuclei. These results suggest that both transcriptional and post-transcriptional regulation may be operative in the expression of alpha and beta MHC genes during the development of cardiac hypertrophy.
对从大鼠心脏细胞核转运来的RNA进行体外翻译表明，来自肥厚心脏细胞核的可翻译信息的转运量大于假手术心脏细胞核的转运量。在无细胞体系中，当存在肥厚心脏细胞溶胶时，与来自假手术心脏细胞溶胶相比，从假手术心脏细胞核转运来的RNA具有更高的翻译活性。当使用β cDNA探针通过狭缝印迹杂交分析转运RNA中的肌球蛋白重链（MHC）mRNA时，也得到了类似的结果。使用β MHC同工酶特异性抗体对翻译产物进行免疫沉淀分析表明，在存在肥厚心脏细胞溶胶时，从假手术心脏细胞核转运来的RNA中β MHC特异性mRNA的水平高于假手术心脏细胞溶胶中的水平。使用与α和β MHC mRNA的3'非翻译区对应的寡聚探针通过狭缝印迹杂交分析转运RNA，直接定量α和β MHC信使RNA，结果显示在存在肥厚心脏细胞溶胶时，从假手术心脏细胞核转运来的α和β MHC特异性mRNA均增加，其中β MHC mRNA的增加量大于α MHC。相反，对从假手术和肥厚心脏获得的细胞核中体外转录过程中合成的放射性RNA进行狭缝印迹杂交分析表明，假手术细胞核中α的合成增加，肥厚心脏细胞核中β的合成增加。这些结果表明，在心肌肥厚发展过程中，α和β MHC基因的表达可能同时受到转录和转录后调控。
