Identification of two RNA-binding proteins associated with human telomerase RNA

Telomerase plays a crucial role in telomere maintenance in vivo. To underst and telomerase regulation,we have been characterizing components of the enz yme. To date several components of the mammalian telomerase holoenzyme have been identified: the essential RNA component (human telomerase RNA [hTR]), the catalytic subunit human telomerase reverse transcriptase (hTERT), and telomerase-associated protein 1. Here we describe the identification of two new proteins that interact with hTR: hStau and L22. Antisera against both proteins immunoprecipitated hTR, hTERT, and telomerase activity from cell e xtracts, suggesting that the proteins are associated with telomerase. Both proteins localized to the nucleolus and cytoplasm. Although these proteins are associated with telomerase, we found no evidence of their association w ith each other or with telomerase-associated protein 1. Both hStau and L22 are more abundant than TERT. This, together with their localization, sugges ts that they may be associated with other ribonucleoprotein complexes in ce lls. We propose that these two hTR-associated proteins may play a role in h TR processing, telomerase assembly, or localization in vivo.