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HGNC Approved Gene Symbol: BTF3
Cytogenetic location: 5q13.2 Genomic coordinates (GRCh38) : 5:73,498,442-73,505,667 (from NCBI)
Several transcription factors are involved in the initiation of transcription from proximal promoter elements such as the TATA box. One such transcription factor is BTF3. Zheng et al. (1990) cloned the human BTF3 gene from a HeLa cell cDNA library. They identified 2 distinct cDNAs, presumed to be alternatively spliced products of a single gene. The 2 cDNAs, termed BTF3a and BTF3a, encode polypeptides of 206 and 162 amino acids with observed masses of 27 and 22 kD, respectively. BTF3b is shorter by 44 amino acids at the N terminus. Zheng et al. (1990) demonstrated that cells transfected with BTF3A, but not BTF3B, express BTF3-mediated transcriptional activity. They also showed that both BTF3a and BTF3b form complexes with RNA polymerase IIB (180661).
By Southern blotting, Kanno et al. (1992) found that BTF3 has at least 3 homologous sequences in the human genome, termed BTF3L1 (602543), BTF3L2 (603738), and BTF3L3 (603739).
Wiedmann et al. (1994) purified the heterodimeric nascent polypeptide-associated complex (NAC) from bovine cytosol and determined that it contains Naca (602542), which migrated at an apparent molecular mass of about 33 kD, and Btf3b, which migrated at an apparent molecular mass of about 21 kD. Using peptide sequences from the purified proteins, they cloned human NACA and BTF3B.
Wiedmann et al. (1994) determined that NAC bound ubiquitously to nascent polypeptides emerging from ribosomes unless a signal peptide was fully exposed. NAC did not bind to fully emerged signal peptides. In the absence of NAC, the signal recognition particle (SRP; see 604857) interacted with polypeptides even in the absence of a signal peptide and allowed mistargeting of the protein to the SRP receptor (see 600867) at the endoplasmic reticulum membrane. Readdition of purified NAC prevented mistranslocation.
Bloss et al. (2003) reported that the C. elegans inhibitor of cell death-1 (ICD1) is necessary and sufficient to prevent apoptosis. Loss of ICD1 leads to inappropriate apoptosis in developing and differentiated cells in various tissues. Although this apoptosis requires CED4, it occurs independently of CED3, the caspase essential for developmental apoptosis, showing that these core proapoptotic proteins have separable roles. Overexpression of ICD1 inhibited the apoptosis of cells that are normally programmed to die. ICD1 is the beta-subunit of the nascent polypeptide-associated complex (beta-NAC) and contains a putative caspase cleavage site and caspase recruitment domain. It localizes primarily to mitochondria, underscoring the role of mitochondria in coordinating apoptosis. Human beta-NAC is a caspase substrate that is rapidly eliminated in dying cells (Brockstedt et al., 1999; Thiede et al., 2001), suggesting that ICD1 apoptosis-suppressing activity may be inactivated by caspases.
Kanno et al. (1992) examined the genomic structure of the BTF3 gene. They confirmed that BTF3a and BTF3b are the products of alternative splicing. The gene has 7 exons spanning approximately 7 kb of the genome. Exon 1 is the 3-prime noncoding region; the start codons for BTF3a and BTF3b are on exons 2 and 3, respectively.
Bloss, T. A., Witze, E. S., Rothman, J. H. Suppression of CED-3-independent apoptosis by mitochondrial beta-NAC in Caenorhabditis elegans. Nature 424: 1066-1071, 2003. [PubMed: 12944970] [Full Text: https://doi.org/10.1038/nature01920]
Brockstedt, E., Otto, A., Rickers, A., Bommert, K., Wittmann-Liebold, B. Preparative high-resolution two-dimensional electrophoresis enables the identification of RNA polymerase B transcription factor 3 as an apoptosis-associated protein in the human BL60-2 Burkitt lymphoma cell line. J. Protein Chem. 18: 225-231, 1999. [PubMed: 10333297] [Full Text: https://doi.org/10.1023/a:1020636308270]
Kanno, M., Chalut, C., Egly, J.-M. Genomic structure of the putative BTF3 transcription factor. Gene 117: 219-228, 1992. [PubMed: 1386332] [Full Text: https://doi.org/10.1016/0378-1119(92)90732-5]
Thiede, B., Dimmler, C., Siejak, F., Rudel, T. Predominant identification of RNA-binding proteins in Fas-induced apoptosis by proteome analysis. J. Biol. Chem. 276: 26044-26050, 2001. [PubMed: 11352910] [Full Text: https://doi.org/10.1074/jbc.M101062200]
Wiedmann, B., Sakai, H., Davis, T. A., Wiedmann, M. A protein complex required for signal-sequence-specific sorting and translocation. Nature 370: 434-440, 1994. [PubMed: 8047162] [Full Text: https://doi.org/10.1038/370434a0]
Zheng, X. M., Black, D., Chambon, P., Egly, J. M. Sequencing and expression of complementary DNA for the general transcription factor BTF3. Nature 344: 556-559, 1990. [PubMed: 2320128] [Full Text: https://doi.org/10.1038/344556a0]