VIRAL SMALL RNPS AND CELL TRANSFORMATION

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DESCRIPTION: (Applicant's Description) The roles of small nuclear RNA- protein (snRNP) complexes found in lymphoid cells transformed by two herpesviruses are being investigated. Epstein-Barr virus infects and transforms human B cells and is the causative agent of infectious mononucleosis, as well as being associated with several human cancers. Herpesvirus saimiri induces fatal lymphomas and leukemias in New World monkeys and transforms human and monkey T lymphocytes and leukemias in New World monkeys and transforms human and monkey T lymphocytes in culture. Among the few viral gene products expressed in transformed cells are the two EBV-encoded EBERs and the seven H. saimiri-encoded HSURs. These small nuclear RNAs are abundant, conserved, and associate with host auto-antigens that are components of cellular snRNPs. Yet, both EBERs and HSURs are non-essential for viral growth of transformation. Proposed experiments are based on the hypothesis that EBERs and HSURs perturb cellular metabolism by sequestering important host proteins, thereby facilitating transformation. EBER1 binds a significant fraction of the host's ribosomal protein L22, whose is involved in chromosomal translocations in some patients with acute myeloid leukemia. Consequences of EBER1 interaction with L22 will be studied by locating the L22 binding site in the 60S ribosome and asking whether L22-depleted ribosomes enhance the read-through of upstream AUGs in nuclear antigen (EBNA) mRNAs to increase their translation during latency. HSURs 1, 2, and 5 have AU3A motifs at their 5' ends that bind HuR, a host protein whose over-expression stabilizes the normally short-lived mRNAs for proto-oncogenes, cytokines and lymphokines. HUR's nucleo- cytoplasmic shuttling motif and its interactions with several protein phosphatase 2A (PP2A) inhibitors, one of which is reported to have tumor suppressor activity will be dissected by mutational analyses. The subcellular location of AU3A-directed RNA decay and the possibility that HuR and hnRNPD play opposing roles in MRNA stability will be investigated. The expression of human papillomavirus E6/E7 oncoproteins will be studied to establish whether the PP2A inhibitors and HuR are components of a phosphorylation cascade regulating mRNA stability. The mechanism of AU3A-directed mRNA deadenylation/decay and its regulation during early development will be studied in the Xenopus system. Clues to the functions of the EBER2 and HSUR 3, 4, 6 and 7 snRNPs will be sought by identifying interaction proteins.