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The papovavirus SV40 is able to induce tumours in susceptible hosts and will transform cells in vitro. Its major early protein, large T antigen, is required for viral DNA synthesis, both in vivo and in vitro, and is also responsible for the oncogenic action of the virus. We have made use of an extensive library of anti-T monoclonal antibodies to investigate the cellular effects of T. Large T shares an antigenic determinant with a growth-regulated host protein, p68, which is a member of an expanding super-family of helicases with particular homology to the translation initiation factor elF-4A. We have also studied the binding and interaction of large T with two particular host components: the replicative enzyme DNA polymerase α and the proto-oncogene p53. These two proteins bind to similar regions of T and exert similar effects on its antigenic structure. We found that p53 can block the binding of DNA polyrnerase a to T as well as co-existing with DNA polymerase α in a trimeric complex with T. This suggests that these interactions may be important in the oncogenic and replicative action of large T. [ABSTRACT FROM AUTHOR]

A transactivation motif has been identified in the neurodegenerative disease protein, CLN3. The C-terminal domain (residues 394–438) of CLN3 can function as a transcriptional activator when fused to the DNA binding domain, LexA. A series of deletion and substitution constructs have been generated to identify the essential region for transactivation. A similar motif is also present in the POU domain transcription factor, nubbin. However, this domain alone does not activate transcription, allowing further localisation of the critical residues in CLN3 required for activity. [ABSTRACT FROM AUTHOR]