Transcription, biological systems

The lack of zinc can also be a problem in biological systems and is responsible for disease states. For example, nitric oxide-dependent apoptosis can be induced in motor neurons by zinc-deficient SOD, and in some cases of amyotrophic lateral sclerosis, zinc-deficient SOD may participate in this type of oxidative mechanism involving nitric oxide.969 One form of hereditary human hair loss or alopecia was mapped to a specific gene and a mutation found in affected individuals. The gene encodes a single zinc finger transcription factor protein with restricted expression in the brain and skin.970 Zinc has been implicated in Alzheimer s via beta amyloid formation, and a role has been attributed for the cerebral zinc metabolism in the neuropathogenesis of Alzheimer s disease.971... 

The major direction of information flow in biological systems is from DNA to RNA to protein. However, there are instances in which RNA is copied into a complementary DNA strand by the process dubbed reverse transcription by the enzyme known as the reverse transcriptase . This mechanism is used by retroviruses including the HIV virus, whose infectious particles contain RNA as the genetic material. The virus particles contain a virally encoded reverse transcriptase which, following infection, copies the viral RNA into DNA. The resultant DNA copy is incorporated into the genome of the infected cell. 

Information transfer in biological systems usually involves transfer from DNA to DNA (DNA replication), DNA to RNA (transcription) and RNA to protein (translation). Most RNA viruses have an additional mode of passing information RNA to RNA (RNA replication). RNA tumor viruses have yet another additional way of passing information RNA to DNA (reverse transcription). 

Retinoic acid is involved in only two of the known functions of Vitamin A, namely growth and cellular differentiation. Retinoic acid is a potent inducer of cellular differentiation, in vitro (17-191. and may be necessary for normal gene expression (17.271. Several nuclear transcription factors for retinoic acid have been identified (28.291 and the associated genes products may be necessary to prevent cellular transformation. Therefore, retinoic acid may be necessary for homeostasis. However, because of its potency, it exists in low concentrations in biological systems. 

Metalloporphyrins, characterized by a redox-active transitional metal coordinated to a cyclic porphyrin core ligand, mitigate oxidative/nitrosative stress in biological systems. Side-chain substitutions tune redox properties of metalloporphyrins to act as potent superoxide dismutase mimetics, peroxynitrite decomposition catalysts, and redox regulators of transcription factor function. Metalloporphyrins are efficacious in AD models [538],... 

Information Flow in Biological Systems Classes of RNA Molecules Transcription Post-transcriptional... 

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