Cloning of two isoforms of mouse DNA helicase Q1 RecQL cDNA; alpha form isexpressed ubiquitously and beta form specifically in the testis

We cloned cDNAs encoding mouse homologues for the human DNA helicase Q1/Rec QL (human helicase Q1) which has homology with the Escherichia coli RecQ pr otein and found that they encode two isoforms. The two isoforms are identic al over the entire sequence except for the carboxyl terminal sequence spann ing less than 30 amino acids. One of the two isoforms, alpha, contains a se quence, KKRK, in the carboxyl terminus, which is also contained in human he licase Q1 and was confirmed to function as the nuclear localization signal. The other form, beta, does not contain such a sequence. Expression of mous e helicase Q1 mRNA is extremely and relatively high in the testis and the t hymus, respectively. RT-PCR analysis revealed that helicase Q1 alpha was ex pressed in all tissues tested and the beta form was expressed only in the t estis. A survey of expression of Q1 alpha and Q1 beta mRNA in the testis af ter birth revealed that Q1 alpha mRNA is expressed in all testes of mice ag ed from 7 days to 8 weeks, and the expression of Q1 beta mRNA begins 14 day s after birth, corresponding to the appearance of cells in the pachytene st age. (C) 1998 Elsevier Science B.V. All rights reserved.