The Drosophila gene grainyhead is the founding member of a large family of genes encoding developmental transcription factors that are highly conserved from fly to human. The family consists of two main branches, with grainyhead as the ancestral gene for one branch and the recently cloned DrosophilaCP2 as the ancestral gene for the other. We now extend this family with the identification of another novel mammalian member, Sister-of-Mammalian Grainyhead (SOM), which is phylogenetically aligned with grainyhead. SOM is closely related to the other mammalian homologues of grainyhead, including Mammalian Grainyhead (MGR) and Brother-of-MGR, sharing a high degree of sequence identity with these factors in the functional DNA-binding, protein dimerization and activation domains. Protein interaction studies demonstrate that SOM can heterodimerize with MGR and Brother-of-MGR, but not with the more distant members of the family. Like grainyhead, the SOM gene too produces several distinct isoforms with differing functional properties through alternative splicing. The tissue distributions of these isoforms differ and all display highly restricted expression patterns. These findings indicate that SOM, like its family members, may play important roles in mammalian development.
Abbreviations used: BOM, Brother-of-MGR; CAT, chloramphenicol acetyltransferase; EST, expressed sequence tag; GRH, Drosophila Grainyhead; GST, glutathione S-transferase; MGR, Mammalian Grainyhead; RACE, rapid amplification of cDNA ends; RT, reverse transcriptase; SCL, stem cell leukaemia; SOM, Sister-of-MGR.
The nucleotide sequence data for human SOM have been submitted to the DDBJ, EMBL, GenBank® and GSDB Nucleotide Sequence Databases. The accession number is pending.