SMG6 Homolog, Nonsense Mediated mRNA Decay Factor (SMG6)

EST1A associated with telomerase activity in human cell lines and bound human TERT in rabbit reticulocyte lysates. In contrast to yeast Est1, EST1A bound TERT independently of telomerase RNA (TERC). An N-terminal region of EST1A bound yeast telomeric single-stranded DNA and, more weakly, human telomeric DNA. Transfection of human embryonic kidney cells with EST1A led to decreased average telomere length, whereas cotransfection of EST1A with TERT resulted in telomere lengths that exceeded those of cells expressing TERT alone. The deduced 1,388-amino acid protein has a central Est1 homology domain containing 2 tetratricopeptide repeat (TPR) motifs and a C-terminal PIN domain, which may be involved in nucleic acid binding or nuclease activity. A 7.5-kb EST1A transcript was ubiquitously expressed.