Quá trình tổng hợp một phân tử RNA từ DNA là một quá trình phức tạp liên quan đến một trong các nhóm của enzyme RNA polymerase và một số protein liên quan. Các bước chung cần thiết để tổng hợp bảng điểm chính là bắt đầu, kéo dài, và chấm dứt. Nhất là biết về bắt đầu. | RNA Synthesis Processing Modification 37 Daryl K. Granner MD P. Anthony Weil PhD BIOMEDICAL IMPORTANCE The synthesis of an RNA molecule from DNA is a complex process involving one of the group of RNA polymerase enzymes and a number of associated proteins. The general steps required to synthesize the primary transcript are initiation elongation and termination. Most is known about initiation. A number of DNA regions generally located upstream from the initiation site and protein factors that bind to these sequences to regulate the initiation of transcription have been identified. Certain RNAs mRNAs in particular have very different life spans in a cell. It is important to understand the basic principles of messenger RNA synthesis and metabolism for modulation of this process results in altered rates of protein synthesis and thus a variety of metabolic changes. This is how all organisms adapt to changes of environment. It is also how differentiated cell structures and functions are established and maintained. The RNA molecules synthesized in mammalian cells are made as precursor molecules that have to be processed into mature active RNA. Errors or changes in synthesis processing and splicing of mRNA transcripts are a cause of disease. RNA EXISTS IN FOUR MAJOR CLASSES All eukaryotic cells have four major classes of RNA ribosomal RNA rRNA messenger RNA mRNA transfer RNA tRNA and small nuclear RNA snRNA . The first three are involved in protein synthesis and snRNA is involved in mRNA splicing. As shown in Table 37-1 these various classes of RNA are different in their diversity stability and abundance in cells. RNA IS SYNTHESIZED FROM A DNA TEMPLATE BY AN RNA POLYMERASE The processes of DNA and RNA synthesis are similar in that they involve 1 the general steps of initiation elongation and termination with 5 to 3 polarity 2 large multicomponent initiation complexes and 3 adherence to Watson-Crick base-pairing rules. These processes differ in several important ways .
