Regions required for chicken glycine decarboxylase gene transcription were examined. A region between -82 and +22 (-82/+22) with motifs similar to binding sites for Sp1, NF-Y and CP2 was assigned to the proximal promoter active in both chicken hepatoma cell line, LMH, and hepatocytes in primary culture. In LMH cells, a genomic region, KX, between KpnI (-4155) and XbaI (-2113) sites changed promoter activity with the aid of four additional genomic regions termed upstream regulator regions for suppression (UpRS) and activation (UpRA) of transcription. Those precise segments are UpR1S (-376/-346), UpR1A (-345/-291), UpR2S (-137/-108) and UpR2A (-107/-83). Within KX, -4155/-3605 activates and -3604/-3367 suppresses the promoter. -3366/-3024 activates or suppresses the promoter, probably with different UpR counterparts. -2197/-2113 restores the actions of -3366/-3024. While in LMH cells, the upstream UpRs abrogate the functions of immediately downstream UpRs, UpR1S or UpR2S or both may be at least less active in hepatocytes than in LMH cells. Nuclear extracts from various chicken tissues and LMH cells had UpR2A binding proteins in different populations, suggesting that together with the UpRs, the segments in KX are involved in the regulation of cell type-specific transcription of this gene.