The conserved core enzymatic activities and the distinct dynamics of polyomavirus large T antigens

Abstract

Several human polyomaviruses including JCV, BKV and TSV are associated with diseases, particularly in immunosuppressed patients. While the large T antigen (LT) encoded by the monkey polyomavirus SV40 is well studied, and possesses intrinsic ATPase and DNA helicase activities, the LTs of the human polyomaviruses are relatively uncharacterized. In order to evaluate whether these enzymatic activities, which are required for viral DNA replication, are conserved between polyomaviruses, we performed a comparative study using the LTs from JCV, TSV and SV40. The ATPase and DNA helicase activities and the interaction with the cellular tumor suppressor p53 were assayed for the purified Zn-ATPase domains of the three LTs. We found that all Zn-ATPases were active ATPases. The Zn-ATPase domains also functioned as DNA helicases, although the measured kinetic constants differed among the three proteins. In addition, when tested against four small molecule ATPase inhibitors, the Zn-ATPase domains of TSV was more resistant than that of SV40 and JCV. Our results show that, while LTs from JCV and TSV share the core ATPase and DNA helicase activities, they possess important functional differences that might translate into their respective abilities to infect and replicate in hosts.

Dysregulation of the MEK/ERK/MNK1 signalling cascade by middle T antigen of the trichoydsplasia spinulosa polyomavirus

“…4 While TSPyV LT is known to contain highly pathogenic sequences resembling the AAA+ (ATPases Associated with various cellular Activities) superfamily in addition to binding domains for p53 and pRB, the role of LT antigen in TS disease progression remains questionable. 15 Notably, in vitro analysis of TSPyV LT function demonstrates the absence of helicase activity (associated with AAA+) and minimal p53 interaction. 15 Thus, a specific function for LT antigen in the context of TS has not yet been established.…”

“…15 Notably, in vitro analysis of TSPyV LT function demonstrates the absence of helicase activity (associated with AAA+) and minimal p53 interaction. 15 Thus, a specific function for LT antigen in the context of TS has not yet been established. In contrast to LT, several lines of evidence have implicated TSPyV sT antigen in processes that may drive cell proliferation.…”

Molecular insight into the viral biology and clinical features of trichodysplasia spinulosa

“…Among these, the LT and sT antigens have been studied more extensively and are known to contain many characteristic protein‐binding motifs that are conserved among all polyomaviruses. Notably, initial genomic studies suggested that TSPyV LT contained binding domains for p53 and retinoblastoma family proteins (pRb, p107 and p130), in addition to sequences characteristic of the AAA+ (ATPases associated with various cellular activities) superfamily . These proteins function in concert to regulate DNA replication; while p53 and Rb tumour suppressors are essential to G1/S regulation and DNA repair mechanisms, AAA+ family proteins stimulate ATP hydrolysis to promote helicase activity .…”

“…However, despite the high level of sequence conservation among polyomavirus LT antigens, the cellular functions of TSPyV LT seem to be distinct from those of SV40. To this end, TSPyV LT does not bind p53 or affect helicase activity in vitro . In fact, investigation of the TSPyV LT antigen has yet to establish a clear mechanism associated with pathogenesis.…”

Animal Models for Progressive Multifocal Leukoencephalopathy

“…They are thought to involve a number of cellular transcription factors which include NF‐1 (Monaco et al, ), Egr1 (Romagnoli et al, ), NF‐κB (Romagnoli et al, ), C/EBPβ (Romagnoli et al, ), NFAT4 (Wollebo et al, ), SpiB (Meira et al, ), and others. Similarly, the molecular mechanism of JCV DNA replication is also complex (An et al, ).…”