spliceosome RNA helicase DDX39B; 56 kD U2AF65-associated protein; ATP-dependent RNA helicase p47; DEAD box protein UAP56; HLA-B-associated transcript 1 protein (DDX39B BAT1 UAP56)

Function

• component of the THO subcomplex of the TREX complex
• splice factor required for the first ATP- dependent step in spliceosome assembly & for the interaction of U2 snRNP with the branchpoint
• has both RNA-stimulated ATP binding/hydrolysis activity & ATP-dependent RNA unwinding activity
• even with the stimulation of RNA, the ATPase activity is weak
• can only hydrolyze ATP but not other NTPs
• the RNA stimulation of ATPase activity does not have a strong preference for the sequence & length of the RNA
• however, ssRNA stimulates the ATPase activity much more strongly than dsRNA
• can unwind 5' or 3' overhangs or blunt end RNA duplexes in vitro
• the ATPase & helicase activities are not influenced by U2AF2 & THOC4
• homodimer, & heterodimer with DDX39A
• component of the spliceosome
• interacts directly with U2AF2
• interacts directly with THOC4 & is necessARy for THOC4 recruitment to spliced mRNA
• interacts with RBM8A, RNPS1 & SRRM1
• interacts with FYTTD1/UIF & THOC1

Kinetic parameters:

• KM=3.3 uM for ATP
• Vmax=0.126 uM/min/mg enzyme with ATP as substrate

Structure

• the helicase C-terminal domain mediates interaction with THOC4
• belongs to the DEAD box helicase family, DECD subfamily
• contains 1 helicase ATP-binding domain
• contains 1 helicase C-terminal domain

Compartment

nucleus, nuclear speckle

Alternative splicing

named isoforms=2

More general terms

• DEAD box ATP-dependent helicase
• phosphoprotein

Component of

• THO subcomplex
• spliceosome

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=7919
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:7919
• OMIM: https://mirror.omim.org/entry/142560
• UniProt: http://www.uniprot.org/uniprot/Q13838.html