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The 193-kD vault protein, VPARP, a novel poly(ADP-ribose) polymerase (PARP), is discussed. The 19d-kD vault protein has been identified and characterized by by peptide sequence analysis and by interaction with MVP, the 100-k major vault protein, in a yeast two-hybrid screen. One substrate for a vault-associated PARP activity was found in the study to be the MVP. Data show that p193 protein is not entirely associated with the vault particle. Thus the vault particle may interact with other proteins.

Vaults and telomerase are ribonucleoprotein (RNP) particles that share a common protein subunit, TEP1. Although its role in either complex has not yet been defined, TEP1 has been shown to interact with the mouse telomerase RNA and with several of the human vault RNAs in a yeast three-hybrid assay. An m [Tep1.sup.-/-] mouse was previously generated which resulted in no apparent change in telomere length or telomerase activity in six generations of m Tep1-deficient mice. Here we show that the levels of the telomerase RNA and its association with the telomerase RNP are also unaffected in m [Tep1.sup.-/-] mice. Although vaults purified from the livers of m [Tep1.sup.1-/-] mice appear structurally intact by both negative stain and cryoelectron microscopy, three-dimensional reconstruction of the m [Tep1.sup.-/-] vault revealed less density in the cap than previously observed for the intact rat vault. Furthermore, the absence of TEP1 completely disrupted the stable association of the vault RNA with the purified vault particle and also resulted in a decrease in the levels and stability of the vault RNA. Therefore, we have uncovered a novel role for TEP1 in vivo as an integral vault protein important for the stabilization and recruitment of the vault RNA to the vault particle. Key words: TEP1 * vaults * mouse embryonic stem cells * RNA stability * cryo-EM

Investigates the in vivo role of TEP1 protein in the stabilization and recruitment of the vault RNA to the vault particle. Role of TEP1 in the telomerase/vault complex; Effect of three-dimensional reconstruction cap density of mutant Tep1; Components of the cytoplasmic ribonucleoprotein complexes.