ID   ST_POVBA                Reviewed;         172 AA.
AC   P15000;
DT   01-APR-1990, integrated into UniProtKB/Swiss-Prot.
DT   01-APR-1990, sequence version 1.
DT   29-SEP-2021, entry version 89.
DE   RecName: Full=Small t antigen;
DE            Short=ST;
DE            Short=ST-AG;
OS   BK polyomavirus (strain AS) (BKPyV).
OC   Viruses; Monodnaviria; Shotokuvirae; Cossaviricota; Papovaviricetes;
OC   Sepolyvirales; Polyomaviridae; Betapolyomavirus.
OX   NCBI_TaxID=10631;
OH   NCBI_TaxID=9606; Homo sapiens (Human).
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RX   PubMed=2536111; DOI=10.1128/jvi.63.2.901-911.1989;
RA   Tavis J.E., Walker D.L., Gardner S.D., Frisque R.J.;
RT   "Nucleotide sequence of the human polyomavirus AS virus, an antigenic
RT   variant of BK virus.";
RL   J. Virol. 63:901-911(1989).
CC   -!- FUNCTION: Promotes efficient viral genome replication by accelerating
CC       both G1 and S phase progression of the cell cycle. Inhibits host PP2A
CC       by binding to the A subunit, thereby displacing lower affinity
CC       regulatory B subunit. Inactivation of PP2A in turn results in the
CC       transactivation of cyclin A and cyclin D1 promoters. Late during the
CC       infection cycle, ST may induce dephosphorylation of host MTOR, leading
CC       to the inhibition of cap-dependent translation. May establish and
CC       maintain high levels of viral genomes during persistent infection in
CC       cell culture. {ECO:0000250|UniProtKB:P03081}.
CC   -!- SUBUNIT: Interacts with host PPP2R1A; the interaction inhibits PP2A
CC       activity. {ECO:0000250|UniProtKB:P03081}.
CC   -!- SUBCELLULAR LOCATION: Host cytoplasm. Host nucleus
CC       {ECO:0000250|UniProtKB:P03081}.
CC   -!- ALTERNATIVE PRODUCTS:
CC       Event=Alternative splicing; Named isoforms=2;
CC       Name=Small t antigen;
CC         IsoId=P15000-1; Sequence=Displayed;
CC       Name=Large T antigen;
CC         IsoId=P14999-1; Sequence=External;
CC   -!- DOMAIN: The common region of ST and LT proteins comprises the J domain.
CC       This domain is essential for multiple viral activities, including
CC       virion assembly, viral DNA replication, transformation and
CC       transcriptional activation. This domain is also required for cyclin A-
CC       transactivating activity of ST. {ECO:0000250|UniProtKB:P03081}.
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DR   EMBL; M23122; AAA46883.1; -; Genomic_DNA.
DR   PIR; B33278; TVVPSS.
DR   SMR; P15000; -.
DR   Proteomes; UP000008166; Genome.
DR   GO; GO:0030430; C:host cell cytoplasm; IEA:UniProtKB-SubCell.
DR   GO; GO:0042025; C:host cell nucleus; IEA:UniProtKB-SubCell.
DR   GO; GO:0046872; F:metal ion binding; IEA:UniProtKB-KW.
DR   CDD; cd06257; DnaJ; 1.
DR   Gene3D; 1.10.287.110; -; 1.
DR   Gene3D; 1.20.120.1860; -; 1.
DR   InterPro; IPR001623; DnaJ_domain.
DR   InterPro; IPR036869; J_dom_sf.
DR   InterPro; IPR003354; Papo_T_antigen.
DR   InterPro; IPR036092; Papo_T_antigensf.
DR   Pfam; PF02380; Papo_T_antigen; 1.
DR   SMART; SM00271; DnaJ; 1.
DR   SUPFAM; SSF161240; SSF161240; 1.
DR   SUPFAM; SSF46565; SSF46565; 1.
DR   PROSITE; PS50076; DNAJ_2; 1.
PE   3: Inferred from homology;
KW   Acetylation; Activator; Alternative splicing; Early protein;
KW   Host cytoplasm; Host nucleus; Host-virus interaction; Metal-binding;
KW   Oncogene; Phosphoprotein; Transcription; Transcription regulation; Zinc;
KW   Zinc-finger.
FT   CHAIN           1..172
FT                   /note="Small t antigen"
FT                   /id="PRO_0000115052"
FT   DOMAIN          12..75
FT                   /note="J"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00286"
FT   ZN_FING         101..114
FT                   /note="C4-type; atypical"
FT   ZN_FING         120..141
FT                   /note="H1C3-type; atypical"
FT   MOD_RES         1
FT                   /note="N-acetylmethionine; by host"
FT                   /evidence="ECO:0000250|UniProtKB:P03081"
SQ   SEQUENCE   172 AA;  20454 MW;  0AB1BE041D1F302D CRC64;
     MDKVLNREES MELMDLLGLE RAAWGNLPLM RKAYLKKCKE FHPDKGGDED KMKRMNTLYK
     KMEQDVKVAH QPDFGTWNSS EVCADFPLCP DTLYCKEWPI CSKKPSVHCP CMLCQLRLRH
     LNRKFLRKEP LVWIDCYCID CFTQWFGLDL TEETLQWWVQ IIGETPFRDL KL