Mutational analyses of the signals involved in the subcellular location of DSCR1

Abstract Background Down syndrome is the most frequent genetic disorder in humans. Rare cases involving partial trisomy of chromosome 21 allowed a small chromosomal region common to all carriers, called Down Syndrome Critical Region (DSCR), to be determined. The DSCR1 gene was identified in this region and is expressed preferentially in the brain, heart and skeletal muscle. Recent studies have shown that DSCR1 belongs to a family of proteins that binds and inhibits calcineurin, a serine-threonine phosphatase. The work reported on herein consisted of a study of the subcellular location of DSCR1 and DSCR1-mutated forms by fusion with a green fluorescent protein, using various cell lines, including human. Results The protein's location was preferentially nuclear, independently of the isoform, cell line and insertion in the GFP's N- or C-terminal. A segment in the C-terminal, which is important in the location of the protein, was identified by deletion. On the other hand, site-directed mutational analyses have indicated the involvement of some serine and threonine residues in this event. Conclusion In this paper, we discuss the identification of amino acids which can be important for subcellular location of DSCR1. The involvement of residues that are prone to phosphorylation suggests that the location and function of DSCR1 may be regulated by kinases and/or phosphatases.

The authors thank Renata ManelliOliveira and Roberto Cabado (ICB, USP, Brazil) for performing the confocal microscopy analyses and César Sommer (DGEUFSCar) for his suggestions and help in revising this manuscript. We are also indebted to the Brazilian research funding institution FAPESP for its grant and financial support for publication (Process #96/110180 and #98/006450).

The authors thank Renata Manelli-Oliveira and Roberto Cabado (ICB, USP, Brazil) for performing the confocal microscopy analyses and César Sommer (DGE-UFSCar) for his suggestions and help in revising this manuscript. We are also indebted to the Brazilian research funding institution FAPESP for its grant and financial support for publication (Process #96/11018-0 and #98/00645-0).