Nucleotide factor

ITowever, most normal somatic cells lack telomerase. Consequently, upon every cycle of cell division when the cell replicates its DNA, about 50-nucleotide portions are lost from the end of each telomere. Thus, over time, the telomeres of somatic cells in animals become shorter and shorter, eventually leading to chromosome instability and cell death. This phenomenon has led some scientists to espouse a telomere theory of aging that implicates telomere shortening as the principal factor in cell, tissue, and even organism aging. Interestingly, cancer cells appear immortal because they continue to reproduce indefinitely. A survey of 20 different tumor types by Geron Corporation of Menlo Park, California, revealed that all contained telomerase activity. 

Cyclic AMP-binding Guanine Nucleotide Exchange Factors... 

Sequence-specific transcription factors often bind as multimers especially as dimers to DNA. This allows binding of mirror-imaged sequences (palindromes) in the DNA that are separated by a few spacer nucleotides. The dimerization is stabilized by hydrophobic motifs within dimerization motifs of each transcription factor molecule. Dependent on the nature of the dimerization domain and the abundance of individual transcription factors homo- or heterodimers can form and bind to palindromes with differential activity. 

The gene promoter is a nucleotide sequence in DNA near the start of a gene, consisting of regulatory elements to which transcription factors and RNA polymerase bind. This leads to activation of the gene promoter and transcription of the corresponding gene. 

Guanine nucleotide exchange factors (GEFs) are proteins which catalyse the release of nucleotide bound to small GTPases. 

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