Nuclear accessory factor

Studies are now underway to elucidate the mechanism of VDR interaction with the VDRE. Liao et al. [251] provided the first evidence that an accessory factor is essential for VDR binding to VDRE, by showing that recombinant VDR does not bind to human osteocalcin VDRE without an accessory factor from nuclear extract. This result was also found by two other independent laboratories [252, 253], The accessory factor, termed nuclear accessory factor (NAF) or receptor auxiliary factor (RAF), is a 55... 

Figure 43-11. The hormone response transcription unit. The hormone response transcription unit is an assembly of DNA elements and bound proteins that interact, through protein-protein interactions, with a number of coactivator or corepressor molecules. An essential component is the hormone response element which binds the ligand (A)-bound receptor (R). Also Important are the accessory factor elements (AFEs) with bound transcription factors. More than two dozen of these accessory factors (AFs), which are often members of the nuclear receptor superfamily, have been linked to hormone effects on transcription. The AFs can interact with each other, with the liganded nuclear receptors, or with coregulators. These components communicate with the basal transcription complex through a coregulator complex that can consist of one or more members of the pi 60, corepressor, mediator-related, or CBP/p300 families (see Table 43-6).

Lin B, Morris DW, Chou JY. Hepatocyte nuclear factor 1 alpha is an accessory factor required for activation of glucose-6-phosphatase gene transcription by glucocorticoids. DNA Cell Biol 1998 17 967. ... 

Naturally, a whole cornucopia of accessory factors regulates splicing and splice site selection [18]. In addition to cis-elements within the RNA, several families of RNA factors control which alternative splicing path is chosen. Well-studied examples include serine-rich (SR) proteins and heterologous nuclear ribonuclear particles (hnRNPs) [19, 20]. SR proteins bind to exonic splicing enhancers (ESEs) or intronic splicing enhancers (ISEs) and aid in recruiting the spliceosome itself. 

The genomes of lentiviruses (Fig. 2B) are more complex, encoding a variety of regulatory accessory proteins and pathogenesis factors that are not present in the genomes of simple retroviruses (103-106). Furthermore, genes encoding proteins that utilize the cellular nuclear import machinery, for example, MA, IN,... 

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