The enzymes of the ubiquitylation pathway play a pivotal role in a number of cellular processes including regulated and targeted proteasomal degradation of substrate proteins. Three classes of enzymes are involved in the process of ubiquitylation; activating enzymes (E1s), conjugating enzymes (E2s) and protein ligases (E3s). UBE2H is a member of the E2 conjugating enzyme family and cloning of the human gene was first described by Kaiser et al. (1994). Human UBE2H shares 54% identity with its yeast homologue (UbcH8) and full length forms of both the human and yeast enzymes showed similar enzymatic activities in vitro by catalyzing the ubiquitylation of histones (Kaiser et al., 1995). In skeletal muscle whole cell extracts TNFα up-regulates and increases the conjugating activity of UBE2H in vitro via binding of NF-κB to the promoter region of the gene (Li et al., 2003). UBE2H has been mapped to a region on chromosome 7 (Hayashida et al., 2000) and the gene has been identified as a candidate for involvement in an autistic disorder with neurodevelopmental complications. Single strand conformation analysis demonstrated a significant association between a polymorphism in the UBE2H gene suggesting it could be one of the 7q-susceptibility loci for Autistic Disorder (Vourc'h et al., 2003). An association has also been made between UBE2H and the motor neuron disorder amyotrophic lateral sclerosis (ALS) where single strand conformation polymorphism (SSCP) analysis identified a known and sporadic polymorphism in the gene (Martin et al., 2008).
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