Component of the shelterin complex (telosome) that is involved in the regulation of telomere length and protection. Shelterin associates with arrays of double-stranded TTAGGG repeats added by telomerase and protects chromosome ends; without its protective activity, telomeres are no longer hidden from the DNA damage surveillance and chromosome ends are inappropriately processed by DNA repair pathways. Plays a role in shelterin complex assembly. Isoform 1 may have additional role in tethering telomeres to the nuclear matrix. Monomer. Found in a complex with POT1; TERF1 and TNKS1. Component of the shelterin complex (telosome) composed of TERF1, TERF2, TINF2, TERF2IP ACD and POT1. Interacts with TERF1, TERF2 and ACD. Associated with telomeres. Experimental confirmation may be lacking for some isoforms. Detected in heart, brain, placenta, lung, liver, skeletal muscle, kidney and pancreas. The TBM domain mediates interaction with TERF1. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry.