The present invention disclosed isolated nucleic acid molecules (polynucleotides) which encode NHL, a putative DNA helicase. The present invention in turn relates to recombinant vectors and recombinant hosts which contain a DNA fragment encoding NHL, substantially purified forms of associated NHL, associated mutant proteins, and methods associated with identifying compounds which modulate NHL, which will be useful in the treatment of various neoplastic disorders. Both a genomic clone containing regulatory and intron sequences, as well as the exon structure and open reading frame of human NHL are disclosed.