AC   MF_04074;
DC   Protein; auto
TR   HAMAP; MF_04074; -; 1; level=0
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Names: HBV_X
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ID   X
DE   RecName: Full=Protein X;
DE   AltName: Full=HBx;
DE   AltName: Full=Peptide X;
DE   AltName: Full=pX;
GN   Name=X;
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CC   -!- FUNCTION: Multifunctional protein that plays a role in silencing host
CC       antiviral defenses and promoting viral transcription. Does not seem to
CC       be essential for HBV infection. May be directly involved in development
CC       of cirrhosis and liver cancer (hepatocellular carcinoma). Most of
CC       cytosolic activities involve modulation of cytosolic calcium. The
CC       effect on apoptosis is controversial depending on the cell types in
CC       which the studies have been conducted. May induce apoptosis by
CC       localizing in mitochondria and causing loss of mitochondrial membrane
CC       potential. May also modulate apoptosis by binding host CFLAR, a key
CC       regulator of the death-inducing signaling complex (DISC). Promotes
CC       viral transcription by using the host E3 ubiquitin ligase DDB1 to
CC       target the SMC5-SMC6 complex to proteasomal degradation. This host
CC       complex would otherwise bind to viral episomal DNA, and prevents its
CC       transcription. Moderately stimulates transcription of many different
CC       viral and cellular transcription elements. Promoters and enhancers
CC       stimulated by HBx contain DNA binding sites for NF-kappa-B, AP-1, AP-2,
CC       c-EBP, ATF/CREB, or the calcium-activated factor NF-AT.
CC   -!- SUBUNIT: May form homodimer. May interact with host CEBPA, CFLAR,
CC       CREB1, DDB1, E4F1, HBXIP, HSPD1/HSP60, NFKBIA, POLR2E and SMAD4.
CC       Interacts with host SMC5-SMC6 complex and induces its degradation.
CC   -!- SUBCELLULAR LOCATION: Host cytoplasm. Host nucleus. Host mitochondrion.
CC       Note=Mainly cytoplasmic as only a fraction is detected in the nucleus.
CC       In cytoplasm, a minor fraction associates with mitochondria or
CC       proteasomes.
CC   -!- PTM: A fraction may be phosphorylated in insect cells and HepG2 cells,
CC       a human hepatoblastoma cell line. Phosphorylated in vitro by host
CC       protein kinase C or mitogen-activated protein kinase. N-acetylated in
CC       insect cells.
CC   -!- SIMILARITY: Belongs to the orthohepadnavirus protein X family.
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DR   Pfam; PF00739; X; 1; trigger=no
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KW   Activation of host NF-kappa-B by virus
KW   Activator
KW   Apoptosis
KW   Host cytoplasm
KW   Host G2/M cell cycle arrest by virus
KW   Host mitochondrion
KW   Host nucleus
KW   Host-virus interaction
KW   Modulation of host cell cycle by virus
KW   Transcription
KW   Transcription regulation
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GO   GO:0033650; C:host cell mitochondrion
GO   GO:0042025; C:host cell nucleus
GO   GO:0085033; P:symbiont-mediated activation of host NF-kappaB cascade
GO   GO:0039592; P:symbiont-mediated arrest of host cell cycle during G2/M transition
GO   GO:0006351; P:DNA-templated transcription
GO   GO:0019079; P:viral genome replication
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FT   From: X_HBVCJ (Q69027)
FT   REGION          68..117
FT                   /note="Mitochondrial targeting sequence"
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Size: 134-154;
Related: None;
Template: Q69027;
Scope:
 Viruses; Orthohepadnavirus
Fusion:
 Nter: None
 Cter: None
Duplicate: None
Plasmid: None
Comments: None
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# Version: 10
# Last updated date: 2024-04-25
# Created date: 2017-05-09
//