An evolutionary rearrangement of the Xp11.3-11.23 region in 3p21.3, a region frequently deleted in a variety of cancers

In searching for a tumor suppressor gene in the 3p21.3 region, we isolated two genes, RBM5 and RBM6. Sequence analysis indicated that these genes shar e similarity. RBM5 and-to a lesser extent-RBM6 also have similarity to DXS8 237E at Xp11.3-11.23, which maps less than 20 kb upstream of UBE1. A homolo gue of UBE1, UBE1L, is located at 3p21.3. FISH analysis showed that the dis tance between UBE1L and RBM5 in 3p21.3 is about 265 kb. DXS8237E and UBE1 o n the X chromosome have the same orientation, whereas on chromosome 3 the o rientation of RBM5 and that of RBM6 are opposite to the orientation of UBE1 L. Presumably, part of the Xp11.3-11.23 region has duplicated to chromosome 3. Part of this region on chromosome 3 may subsequently have duplicated ag ain within the same chromosomal region, Inversion at some stage of the evol ution of the human genome would explain the change in orientation of the ge nes on chromosome 3 compared with that of the genes on the X chromosome. (C ) 1999 Academic Press.