ESCAPE FROM X-INACTIVATION OF 2 NEW GENES ASSOCIATED WITH DXS6974E AND DXS7020E

Most genes on the X chromosome undergo ''inactivation,'' being transcr ibed from only one copy in female somatic cells, but several human gen es have been shown to be expressed from both the active and the otherw ise inactivated homologue. To assess further the fraction and location of genes that escape inactivation, we have analyzed the inactivation status of a set of 73 expressed sequence tags that were derived from t he sequencing of cDNA collections and mapped to the X chromosome. Of 3 3 that were expressed in cultured cells, as assessed by reverse transc ription and PCR, 4 (about 12%) were transcribed from both the active a nd the inactive X chromosome, Two, RPS4 and PCTAIRE1, are already know n to escape inactivation; the other 2, of unknown function, include a short cDNA with a full open reading frame and a transcript with no det ectable open reading frame. They map, respectively, to Xp11.3-p11.4 an d Xp22.2; both regions were previously reported to encode sequences tr anscribed from the inactive X. Neither transcript has a corresponding sequence on the Y. Thus, they exhibit double dosage in females compare d to males, and inactivation status may be inconsequential for these t ranscribed sequences. (C) 1997 Academic Press.