中国生物工程杂志

In prokaryotes and eukaryotes, the regulatory systems are very different and they usually change with the environment. Environmental factors play an important role in gene expression in prokaryotes because every cell in a population of prokaryotes is in direct contact with the environment, which leads to the adaptation by turning certain genes on or off. Therefore, environmental factors are often regulatory effectors, and transcription must be rigorously regulated to ensure that cells respond effectively and adequately to environmental changes. Thus, the regulation of gene expression is crucial to the overall fitness of the cell. The expression of prokaryotic genes is regulated by many factors, and transcription can be roughly divided into three main stages: initiation, extension and termination. For most bacteria, the key steps to regulate gene expression are promoter recognition in the process of transcription initiation and RNA polymerase to initiate transcription. The formation of the transcription initiation complex between RNA polymerase and promoter DNA is the most important regulatory process of bacterial gene expression. Promoters control the transcription of all genes, and the regulation of most promoters is complex. Promoter activity is determined by sequence elements that optimize promoter strength, and strong promoters usually have elements similar to the common sequence. Since the expression level of most transcription units is dependent on environmental inputs, many transcription factors are involved. Transcription factors involve RNA polymerases in different states, promote desired RNA polymerase function and regulate RNA polymerase activity. Each transcription unit is controlled by a regulatory region containing at least one promoter, usually located upstream of the first readable frame. These regulatory regions contain sequence elements that interact with RNA polymerases, as well as binding targets for different transcription factors involved in regulation. Transcription initiation requires the interaction of RNA polymerase with promoter DNA and the formation of an open complex(in order for transcription to occur, the closed promoter complex DNA is double-stranded and must be isomerized into an open promoter complex where the DNA melts into a transcription bubble and the single-stranded template DNA is delivered to the RNA polymerase active site).In bacterial cells, promoter recognition of RNA polymerase is a multi-step process involving multiple protein-DNA interactions and several structural and kinetic intermediates. Therefore, the transcription process of genes can be optimized to adapt to different environmental changes by adjusting the activity of RNA polymerase and changing the binding of RNA polymerase to promoter. Regulation is mediated by a combination of sigma factors, activators, repressors, and transcription factors, as well as by changes in DNA super-helix and local nucleoprotein structure. In this paper, various factors involved in the transcription regulation of bacterial cells have been summarized, and the molecular mechanisms of these factors regulating gene expression are expounded from the aspects of the effects of these factors on promoters, the effects of RNA polymerase and their interactions. This paper aims to summarize the role of various regulation mechanisms, and deepen the understanding of transcription initiation process, in the hope of providing ideas for the future regulation of transcription initiation process to achieve the efficient expression of target genes and the inhibition of the expression of adverse genes, and to provide a basis for the future modification of industrial strains.