TERF2 (telomeric repeat binding factor 2)

	Human TERF2 is alternatively spliced, resulting in 8 protein encoding transcripts. Figure adapted from Flicek et al. 2012.
Description	The human TERF2 gene spans a length of 53011 bp. The TERF2 structural gene is composed of 10 exons.
Transcription	Human TERF2 is alternatively spliced, resulting in 12 transcripts, 8 of which are protein encoding. TERF2-001: 2951 bp in length, with a translational length of 500 residues. TERF2-002: 1112 bp in length, with a translational length of 251 residues. TERF2-003: 554 bp in length, with no protein product. TERF2-004: 556 bp in length, with no protein product. TERF2-005: 513 bp in length, with a translational length of 60 residues; transcript undergoes nonsense-mediated decay. TERF2-006: 917 bp in length, with a translational length of 283 residues. TERF2-008: 791 bp in length, with a translational length of 49 residues. TERF2-009: 573 bp in length, with a translational length of 99 residues; transcript undergoes nonsense mediated decay. TERF2-010: 316 bp in length, with no protein product. TERF2-011: 1107 bp in length, with no protein product. TERF2-012: 431 bp in length, with a translational length of 144 residues. TERF2-013: 669 bp in length, with a translational length of 206 residues. (Flicek et al., 2012).
Pseudogene	This gene has a pseudogene, TERF2IPP1, telomeric repeat binding factor 2 interacting protein pseudogene 1, located on chromosome 22q11.2 (Seal et al., 2011).

	Homodimer. Component of the shelterin complex (telosome) composed of TERF1, TERF2, TIN2, TPP1, RAP1 and POT1. Figure adapted from de Lange 2005, and Oeseburg et al. 2010.
Description	Of the 12 TERF2 transcripts, 8 encode for proteins, and 2 of these are subject to nonsense-mediated decay. Among splice variants: isoform 1 is 500 aa in length, mass 55.6 kDa; isoform 2 is 251 aa in length, mass 28.3 kDa; isoform 6 is 283 aa in length, mass 31.5 kDa; and isoform 13 is 206 aa in length, mass 22.9 kDa (Uhlen et al., 2010).
Expression	Ubiquitous. There are high levels of TERF2 expression in spleen, thymus, prostate, uterus, testes, brain, kidney, lung, liver, small intestine, colon, and peripheral blood leukocytes (Jung et al., 2004; Sugiura et al., 2003; UniProt, 2012).
Localisation	TERF2 colocalizes with telomeric DNA in the nucleus of cells at interphase, and is located at telomeres on chromosome ends during metaphase (Ye et al., 2010). TERF2 has also been found in peripheral nerve axons (Jung et al., 2004).
Function	TERF2 is a component of the telomere-specific protein complex called shelterin or telosome, which coats mammalian telomeric DNA (Kim et al., 2009). TERF2 is a homodimer, which binds to the double-stranded 5'-TTAGGG-3' repeat in telomeres (van Steensel et al., 1998). Its primary role is the maintenance of telomere length, structure, and protection against end-to-end fusion of chromosomes. TERF2 induces the formation of telomere-loops (t-loops); without its protection, telomeres are no longer hidden from DNA repair pathways and these ends could be subject to non-homologous end joining (NHEJ) of chromosomes during metaphase (Wang et al., 2004). TERF2 causes the 3' single-stranded overhang to tuck under the double stranded TTAGGG repeat, thus shielding chromosomes from incorrect processing. TERF2 also works together with the exonuclease Apollo as a negative regulator of telomere length (Ye et al., 2010). TERF2 differs from TERF1 in that its N terminus is basic rather than acidic (provided by RefSeq, Jul 2008).
Homology	Significant TERF2 sequence homology is shared among human (H.sapiens), chimpanzee (P.troglodytes), Rhesus monkey (M.mulatta), dog (C.lupus), cow (B.taurus), mouse (M.musculus), and rat (R.norvegicus). Conserved domains in protein sequences include: the Telomeric Repeat binding Factor domain, the RAP1 binding motif of telomere repeat binding factor, and the 'SWI3, ADA2, N-CoR and TFIIIB' DNA-binding domains, which consist of repeats containing the G/C rich motif (Geer et al., 2010).

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