Exon Sharing of a Novel Human Zinc-Finger Gene, ZIM2, and Paternally Expressed Gene 3 (PEG3)

We have identified a novel human gene, ZIM2 (zinc-finger gene 2 from imprinted domain), located 25 kb downstream of PEG3 (paternally expressed gene 3). ZIM2 produces two different-size transcripts, 2.5 and 9.0 kb in length, with highest levels of expression in adult testis and modest levels in fetal kidney and brain. The 2.5-kb transcript of ZIM2 consists of 11 exons and encodes a Kruppel-type (C2H2) zinc-finger protein with a conserved Kruppel-associated box (KRAB) domain. Rapid amplification of cDNA ends and cDNA sequencing studies showed that ZIM2 and PEG3 transcripts share identical 5′-ends, composed of 7 small exons. Alternative splicing events connect these 7 exons either with the remaining 2 exons of PEG3 or with the remaining 4 exons of ZIM2. Interestingly, the third among the 7 shared exons exhibits sequence similarity to leucine-rich domains that are found at the N-terminal region of a subset of KRAB-containing zinc-finger genes. Sequencing of the 5′-termini of both transcripts indicates that ZIM2 and PEG3 share identical transcription start sites and may also share upstream regulatory elements, although the two genes show distinct patterns of tissue-specific expression.