Putative cDNA clones for a nuclear antigen that crossreacts with anti-human aldolase A monoclonal antibody MAb1A2 were isolated from the HeLa lambda gt11 cDNA library and a candidate clone (clone 3) was analyzed. The cDNA has an open reading frame (ORF) of 1,317 bp encoding a novel RNA helicase belonging to the DEAD RNA helicase family. The ORF also contains a nuclear targeting signal and the epitope for MAb1A2, The putative RNA helicase has sequence similarity to Escherichia coli RNA helicase DEAD, mouse translation factor eIF-4A, and human p68 and p54. (C) 1994 Academic Press, Inc.