We have previously cloned and sequenced a novel zinc finger cDNA, Kid-1 , from the rat. Because of its developmentally regulated expression pattern and its suppression after renal injury, as well as its kindey-predominant expression, we propose that Kid-1 is likely to play an important role in renal gene regulation. Kid-1 encodes a predicted protein with 13 zinc fingers at the carboxy end and Krüppel-associated box (KRAB) A and B regions at the amino terminus. Expression of a Kid-1-GAL4 chimeric protein results in strong transcriptional repression of cotransfected constructs containing GAL4 binding sites and a chloramphenicol acetyl transferase gene driven by either a minimal promoter or a SV40 enhancer. We now report the cloning, structural organization, and chromosomal localization of the Kid-1 gene. The Kid-1 gene is composed of four exons and three introns, closely reflecting the organization of the Kid-1 protein. The KRAB A and B regions are encoded by the second and third exons, respectively. The entire zinc finger region is encoded by the fourth exon. Using a combination of linkage analysis and somatic cell hybrid analysis, Kid-1was mapped to rat chromosome (RNO) 10. Kid-1, Il3, and Sparc form a tight linkage group on RNO10. Regional sublocalization to RNO10q21.3-q22 was established by fluorescence in situ hybridization.