[Regulation of gene expression and recent advance on transcription studies]

Gene expression is governed by multiple cellular processes including transcription, splicing, and translation. Among them, transcriptional regulation is the main regulatory mechanism. Transcription process can be divided into pre-initiation, initiation, elongation and termination, and transcriptional regulation is especially governed through the pre-initiation step. Eukaryotic RNA polymerase alone is not able to initiate specific transcription, but general transcription factors (GTFs) is required for this reaction. In pre-initiation step, many GTFs and RNA polymerase gather at the core promoter of a gene, and form a large initiation complex. There are another class of factors: transcription regulatory factors (TRFs) responsible for the regulation such as tissue-specific/timing-specific transcription and induction/repression of transcription. TRFs directly bind to cis-acting DNA elements which are generally referred enhancers (for activation) or silencers (for repression), and regulate the rate of formation of initiation complex. A TRFs can be divided into at most 4 domains: domains for binding to DNA, regulation of transcription, interaction to other proteins and ligand binding. A number of TRFs can be categorized into rather small numbers of families such as b-zip, Zn-finger, etc. which have a characteristic combination with functional motifs. The third class of transcription factor is referred as a mediator/coactivator, that binds to both TRFs and GTFs, and can transduce the regulatory signal from enhancer to promoter. We can describe many biological processes by a term of transcriptional regulation, such as carcinogenesis, development, morphogenesis, infection and immunity, cell growth and hormone action, etc. However, further studies on chromain/nuclear matrix structure, molecular anatomy of transcription factors, and network of transcription factors are required for understanding of the relationship between biological processes and transcriptional regulation.