A New Cellular Model System for Study of Regulatory Mechanisms of Human Ribosomal Gene Transcription

Abstract

The rate of protein synthesis strictly correlates with the rRNA quantity in a cell. The rRNA synthesis is the first stage in the ribosomal synthesis process. It is actively regulated by such external factors as type of nutrition, growth factor, and cell stress. Thus, pre-rRNA transcription and maturation play a central role in processes of cell growth and proliferation. In recent years, numerous data have been obtained that make it possible to suggest that quantitative and qualitative changes in the rRNA synthesis are the most important molecular indicators of cell malignancy. The principle of suppressing activity of rRNA genes at various stages of their expression is used today in chemotherapeutic methods of treatment of oncological diseases. A number of data indicate that the adaptation of the nucleoli precedes the malignant transformation and is not the result of it. These data offer new possibilities for studying the relationship between the transcription of ribosomal DNA (rDNA) and cell proliferation. Understanding these subtle connections is necessary for the development of new approaches to the molecular characterization and subsequent therapy of neoplastic diseases. The aim of this work was to obtain a cellular model system that makes it possible to adequately estimate the activity of RNA polymerase I in vivo by measuring the expression level of the luciferase reporter gene. For this purpose, the regulatory region of the 6.7 kb rRNA gene preceding the transcriptional start point was recloned into the luciferase expression vector pGL4.77. The obtained construct was used to transfect the line HEK293, which resulted in the line pqA77.HEK293. The new model system opens wide prospects for studying transcription regulation mechanisms of human ribosomal genes.