Induced Expression, Localization, and Chromosome Mapping of a Gene for the TBP-Interacting Protein 120A

TBP-interacting protein 120A (TIP120A) is a novel eukaryotic transcriptional regulator and has been suggested to be involved in the general regulation of transcription because of its ability to potentiate transcription of all classes of genes and to interact with common transcriptional machineries. In the present study, we investigated the expression of the tip120a gene. TIP120A transcripts were expressed abundantly in the heart and liver, moderately in the brain and skeletal muscle, and only slightly in the spleen and lung. This ubiquitous expression pattern was similar to that of TBP. Gene expression of TIP120A in the rat liver was not stimulated by hepatocarcinogenesis or liver regeneration. TIP120A was thus suggested not to be a growth-related protein. On the other hand, in P19 mouse embryonal carcinoma cells, TIP120A expression was elevated upon retinoic acid treatment, which induces differentiation. Notably, the foci-like nuclear localization pattern of TIP120A was transformed into a speckle-like pattern. The level of TIP120A was also elevated in such stem-like cells as F9 and HL60 after each differentiation procedure, retinoic acid and DMSO, respectively. In HEp-2 cells, TIP120A was observed as a limited number of nuclear foci, and the localization coincided with that of the PML oncogenic domain. FISH detection revealed that the human tip120a gene was located at 12q14, the position to which a myopathic type scapuloperoneal syndrome locus also mapped. Our study suggests that, contrary to an early assumption, TIP120A is involved in tissue-specific and/or differentiation-related gene expression.