Gene regulation mechanisms

This gene regulation mechanism has an interesting and very useful practical side. If an investigator introduces into an organism a duplex RNA molecule corresponding in sequence to virtually any mRNA, the Dicer endonuclease cleaves the duplex into short segments,... 

How is gene expression controlled Gene activity is controlled first and foremost at the level of transcription. Whether a gene is transcribed is determined largely by the interplay between specific DNA sequences and the specific proteins that bind to these sequences. We first consider gene regulation mechanisms in prokaryotes and particularly in E. coli, because... 

Pike, J.W., Yamamoto, H. and Shevde, N.K. (2002) Vitamin D receptor-mediated gene regulation mechanisms and current concepts of vitamin D analog selectivity. Advances in Renal Replacement Therapy, 9, 168-174. 

If the above cited data are corroborated in the future, it could serve as one the demonstrative examples of the originality of gene regulation mechanisms and of the action of gene modifiers in eukaryotes on the post-translational level. 

In the 1980s, advances in biotechnology had a considerable impact on steroid research. During this period, the mechanism of steroid hormone-activated gene regulation became more clearly defined. These mechanistic studies stiH receive considerable attention in the primary Hterature. 

Another example is a recently discovered second mode of action by which nuclear receptors modulate transcription. In contrast to DNA-binding-dependent mechanisms, cross talk refers here to gene regulation by protein-protein-interaction of nuclear receptors with other transcription factors, such as AP-1 or NF-kB. Consequently, the nuclear receptor acts as a corepressor or coactivator of transcription. 

Figure 2 The classical activation pathway of SHR. SHRs (gray circle) are associated with chaperones (rectangles). After binding of steroid hormones (black circle) SHRs activate target genes in the nucleus. Additional regulation mechanisms, e.g., phosphorylation are described in the text.

Iron-sulfur centers can participate in regulation mechanisms either directly, when they control the activity of an enzyme, or at a more integrated level, when they modulate the expression of some genes. The regulation mechanisms that have been elucidated so far involve either a change in the redox state or the interconversion of iron—sulfur centers. 

Further studies on the mechanism of resistance of aminoglycoside antibiotics focused on resistance genes existing in antibiotic-producer strains (mainly by Drs. Y. Okami and Kunimoto Hotta), and gradually clarified the relationship between the antibiotic-producing and -regulating mechanism. During this search, indolizomycin (1984) was discovered by cell fusion of two kinds of strains. 

Clearly, the control of gene expression at the transcriptional level is a key regulatory mechanism controlling carotenogenesis in vivo. However, post-transcriptional regulation of carotenoid biosynthesis enzymes has been found in chromoplasts of the daffodil. The enzymes phytoene synthase (PSY) and phytoene desaturase (PDS) are inactive in the soluble fraction of the plastid, but are active when membrane-bound (Al-Babili et al, 1996 Schledz et al, 1996). The presence of inactive proteins indicates that a post-translational regulation mechanism is present and is linked to the redox state of the membrane-bound electron acceptors. In addition, substrate specificity of the P- and e-lycopene cyclases may control the proportions of the p, P and P, e carotenoids in plants (Cunningham et al, 1996). 

Stryer, L., Berg, J.M. and Tymoczko, J.L. (2002). Biochemistry (5th ed.). W.H. Freeman, New York Turner, B.M. (2001). Chromatin and Gene Regulation — Molecular Mechanisms in Epigenetics. Blackwell Science, Oxford... 

Turner, B.M. (2001). Chromatin and Gene Regulation — Molecular Mechanisms in Epigenetics. Blackwell Science, Oxford... 

---