Molecular cloning and characterization of a new fasting-inducible short-chain dehydrogenase/reductase from rat liver(1).

We have isolated a 668 bp cDNA from fasted rat liver, designated RLF98, by suppression subtractive hybridization (SSH). The full-length RLF98 cDNA, cloned by rapid amplification of cDNA ends (RACE), is 1113 bp long with an open reading frame of 912 bp. This cDNA encodes a protein of 303 amino acid residues with a calculated molecular weight of 32433 Da. In vitro transcription and translation of the full-length RLF98 cDNA produced a protein of about 33 kDa. The RLF98 protein shares strong amino acid sequence homology with members of the short-chain dehydrogenase/reductase (SDR) family. Northern analysis of RNA from rat liver revealed a transcript of 1.1 kb. Fasting increased this mRNA 2.7-fold. While the RLF98 gene is widely expressed in rat tissues, its level of expression is highly variable. Expression in liver and kidney is abundant and is more than 10 times that observed in other tissues. Our data indicate that the RLF98 is a new member of the SDR family that is upregulated by fasting. Additional experiments including purification of recombinant RLF98 protein are in progress to define the specific function of this protein and the role it plays during fasting-induced catabolism.