Reviewed, UniProtKB/Swiss-Prot P15000 (ST_POVBA)

Names and origin

Protein names	Recommended name:     Small t antigen       Short name=ST-AG       Short name=ST
Organism	BK polyomavirus (strain AS) (BKPyV) [Complete proteome]
Taxonomic identifier	10631 [NCBI]
Taxonomic lineage	Viruses › dsDNA viruses, no RNA stage › Polyomaviridae › Polyomavirus
Virus host	Homo sapiens (Human) [TaxID: 9606]

Protein attributes

Sequence length	172 AA.
Sequence status	Complete.
Protein existence	Inferred from homology.

General annotation (Comments)

Function	Promotes efficient viral genome replication by accelerating both G1 and S phase progression of the cell cycle. Inhibits host PP2A by binding to the A subunit, thereby displacing lower affinity regulatory B subunit. Inactivation of PP2A in turn results in the transactivation of cyclin A and cyclin D1 promoters. Late during the infection cycle, ST may induce dephosphorylation of host FRAP1, leading to the inhibition of cap-dependent translation. May establish and maintain high levels of viral genomes during persistent infection in cell culture By similarity.
Subunit structure	Interacts with host PPP2R1A; the interaction inhibits PP2A activity By similarity.
Subcellular location	Host cytoplasm. Host nucleus By similarity.
Domain	The common region of ST and LT proteins comprises the J domain. This domain is essential for multiple viral activities, including virion assembly, viral DNA replication, transformation and transcriptional activation. This domain is also required for cyclin A-transactivating activity of ST By similarity.
Sequence similarities	Contains 1 J domain.

Ontologies

Keywords
Biological process	Host-virus interaction Transcription Transcription regulation
Cellular component	Host cytoplasm Host nucleus
Coding sequence diversity	Alternative initiation Alternative splicing
Developmental stage	Early protein
Disease	Oncogene
Domain	Zinc-finger
Ligand	Metal-binding Zinc
Molecular function	Activator
PTM	Acetylation Phosphoprotein
Technical term	Complete proteome
Gene Ontology (GO)
Biological process	interspecies interaction between organisms Inferred from electronic annotation. Source: UniProtKB-KW regulation of transcription Inferred from electronic annotation. Source: UniProtKB-KW transcription Inferred from electronic annotation. Source: UniProtKB-KW
Cellular component	host cell cytoplasm Inferred from electronic annotation. Source: UniProtKB-SubCell host cell nucleus Inferred from electronic annotation. Source: UniProtKB-SubCell
Molecular function	heat shock protein binding Inferred from electronic annotation. Source: InterPro zinc ion binding Inferred from electronic annotation. Source: UniProtKB-KW
Complete GO annotation...

Alternative products

This entry describes 2 isoforms produced by alternative splicing. [Align] [Select]

Isoform Small t antigen (identifier: P15000-1)

This isoform has been chosen as the 'canonical' sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry.

Isoform Large T antigen (identifier: P14999-1)

The sequence of this isoform can be found in the external entry P14999-1.
Isoforms of the same protein are often annotated in two different entries if their sequences differ significantly.

Sequence annotation (Features)

	Feature key	Position(s)	Length	Description	Graphical view	Feature identifier
Molecule processing
	Chain	1 – 172	172	Small t antigen		PRO_0000115052
Regions
	Domain	12 – 75	64	J
	Zinc finger	101 – 114	14	C4-type; atypical
	Zinc finger	120 – 141	22	H1C3-type; atypical
Amino acid modifications
	Modified residue	1	1	N-acetylmethionine; by host By similarity

Sequences

	Sequence		Length	Mass (Da)
	Isoform Small t antigen [UniParc]. Last modified April 1, 1990. Version 1. Checksum: 0AB1BE041D1F302D	FASTA	172	20,454
	10 20 30 40 50 60 MDKVLNREES MELMDLLGLE RAAWGNLPLM RKAYLKKCKE FHPDKGGDED KMKRMNTLYK 70 80 90 100 110 120 KMEQDVKVAH QPDFGTWNSS EVCADFPLCP DTLYCKEWPI CSKKPSVHCP CMLCQLRLRH 130 140 150 160 170 LNRKFLRKEP LVWIDCYCID CFTQWFGLDL TEETLQWWVQ IIGETPFRDL KL
	Isoform Large T antigen. See P14999.	FASTA	–	–

References

[1]	"Nucleotide sequence of the human polyomavirus AS virus, an antigenic variant of BK virus." Tavis J.E., Walker D.L., Gardner S.D., Frisque R.J. J. Virol. 63:901-911(1989) [PubMed: 2536111] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA].

Cross-references

Sequence databases
EMBL GenBank DDBJ	M23122 Genomic DNA. Translation: AAA46883.1.
PIR	TVVPSS. B33278.
3D structure databases
SMR	P15000. Positions 1-170.
ModBase	Search...
Family and domain databases
InterPro	IPR001623. DnaJ_N. IPR003354. Papo_T_antigen. [Graphical view]
Gene3D	G3DSA:1.10.287.110. DnaJ_N. 1 hit.
Pfam	PF00226. DnaJ. 1 hit. PF02380. Papo_T_antigen. 1 hit. [Graphical view]
SMART	SM00271. DnaJ. 1 hit. [Graphical view]
PROSITE	PS00636. DNAJ_1. False negative. PS50076. DNAJ_2. 1 hit. [Graphical view]
ProtoNet	Search...

Entry information

Entry name

ST_POVBA

Accession

Primary (citable) accession number: P15000

Entry history

Integrated into UniProtKB/Swiss-Prot:	April 1, 1990
Last sequence update:	April 1, 1990
Last modified:	January 19, 2010
This is version 43 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

Virus (Virus annotation project)