ID   USF1_XENBO              Reviewed;         307 AA.
AC   Q07957;
DT   01-NOV-1997, integrated into UniProtKB/Swiss-Prot.
DT   01-NOV-1996, sequence version 1.
DT   25-MAY-2022, entry version 89.
DE   RecName: Full=Upstream stimulatory factor 1;
DE            Short=USF;
DE   AltName: Full=B1 factor;
DE   AltName: Full=SPF1;
GN   Name=usf1;
OS   Xenopus borealis (Kenyan clawed frog).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Amphibia;
OC   Batrachia; Anura; Pipoidea; Pipidae; Xenopodinae; Xenopus; Xenopus.
OX   NCBI_TaxID=8354;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   TISSUE=Ovary;
RX   PubMed=1986236; DOI=10.1128/mcb.11.1.412-424.1991;
RA   Kaulen H., Pognonec P., Gregor P.D., Roeder R.G.;
RT   "The Xenopus B1 factor is closely related to the mammalian activator USF
RT   and is implicated in the developmental regulation of TFIIIA gene
RT   expression.";
RL   Mol. Cell. Biol. 11:412-424(1991).
CC   -!- FUNCTION: May act as a regulator of transcription factor IIIA (TFIIIA)
CC       gene expression.
CC   -!- SUBUNIT: Efficient DNA binding requires dimerization with another bHLH
CC       protein. Binds DNA as a homodimer or a heterodimer.
CC   -!- SUBCELLULAR LOCATION: Nucleus.
CC   -!- TISSUE SPECIFICITY: Oocyte and somatic tissue. Oocytic and somatic
CC       forms of this protein exist, probably as a result of post-translational
CC       modifications or minor splicing differences.
CC   -!- DEVELOPMENTAL STAGE: In the oocyte, the protein accumulates from stage
CC       1 to stage 5/6 of oogenesis and persists through gastrulation while the
CC       somatic protein begins to accumulate at early cleavage and, by the
CC       neurula stage, is the dominant, if not exclusive, form present.
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DR   EMBL; M63663; AAA49651.1; -; mRNA.
DR   EMBL; M63664; AAA49652.1; -; mRNA.
DR   PIR; A39674; A39674.
DR   AlphaFoldDB; Q07957; -.
DR   SMR; Q07957; -.
DR   GO; GO:0005634; C:nucleus; IEA:UniProtKB-SubCell.
DR   GO; GO:0003677; F:DNA binding; IEA:UniProtKB-KW.
DR   GO; GO:0046983; F:protein dimerization activity; IEA:InterPro.
DR   Gene3D; 4.10.280.10; -; 1.
DR   InterPro; IPR011598; bHLH_dom.
DR   InterPro; IPR036638; HLH_DNA-bd_sf.
DR   Pfam; PF00010; HLH; 1.
DR   SMART; SM00353; HLH; 1.
DR   SUPFAM; SSF47459; SSF47459; 1.
DR   PROSITE; PS50888; BHLH; 1.
PE   2: Evidence at transcript level;
KW   DNA-binding; Nucleus; Transcription; Transcription regulation.
FT   CHAIN           1..307
FT                   /note="Upstream stimulatory factor 1"
FT                   /id="PRO_0000127499"
FT   DOMAIN          196..251
FT                   /note="bHLH"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00981"
FT   REGION          104..131
FT                   /note="Disordered"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   REGION          168..207
FT                   /note="Disordered"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   REGION          268..289
FT                   /note="Leucine-zipper"
FT   COMPBIAS        187..207
FT                   /note="Basic and acidic residues"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
SQ   SEQUENCE   307 AA;  33565 MW;  FACA6C08F1C4CEE5 CRC64;
     MKGQQKVADI EEGTVRVQEE GAVATGEDPT SVAIASIQSA ATFSDPNVKY VFRTENGGAQ
     VMYRVIQVAE GQLDGQTEGT GAISGFPATQ SMTQAVIQGA FTSDDNGETD ASGPETHYTY
     FPTDSSTSVG GTPTTVVTTH NSDTLLGQAA STGTGQFYVM MSSQDVLQGG SQRSIAPRTH
     PYSPKSDGPR TTRDDKRRAQ HNEVERRRRD KINNWIVQLS KIIPDCSMES TKTGQSKGGI
     LSKACDYIQE LRQSNLRLSE ELQNLDQLQM DNEVLRQQVE DLKNNNLTLR TQLRHHGVEI
     IIKSDTH