The human-specific Yp11.2/Xq21.3 homology block encodes a potentially functional testis-specific TGIF-like retroposon.
Yp11.2/Xq21.3 is a human-specific homology block that constitutes the largest shared region among the sex chromosomes, spanning some 3.5 Mb. Only two transcribed sequences have been mapped to this segment: the protocadherin genes PCDHX/Y, and the X-linked poly(A)-binding protein PABPC5 gene, whose Y-homolog has been lost during human evolution. This paper reports the genomic structure, expression, and evolutionary conservation of a third (X-Y homologous) transcribed sequence, TGIFLX/Y (TGIF-like X/Y), mapping to this region. TGIFLX/Y has a 2666-bp mRNA encoded by two exons separated by a 96-bp intron. TGIFLX/Y are homeodomain-containing genes related to the TALE superclass gene family. Comparative DNA analysis indicates that TGIFLX originated from retrotransposition of TGIF2, located on 20q11.2-12, onto the X Chromosome. RT-PCR analysis reveals that both X- and Y-linked genes are specifically expressed in adult testis. Cloning and sequencing of TGIFLX homologs in hominoids and Old World monkeys provides evidence for an open reading frame in the eight species studied. Interestingly, a single base pair deletion in the human TGIFLY (as compared with TGIFLX) creates a different reading frame where the C-terminal residues shared by TGIFLX and other TGIF proteins are missing. The conservation, similarity to protein-encoding transcription factors, and specific expression in testis points to a transcriptional role for TGIFLX/Y in this tissue.
Blanco-Arias
Patricia
P
Human Molecular Genetics Group, Division of Cellular and Molecular Pathology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
Sargent
Carole A
CA
Affara
Nabeel A
NA
D000595:Amino Acid Sequence; D002874:Chromosome Mapping; D041321:Chromosomes, Human, X; D041322:Chromosomes, Human, Y; D019143:Evolution, Molecular; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics; D018626:Retroelements; D013737:Testis / Q000502:physiology*
D018398:Homeodomain Proteins; D012097:Repressor Proteins; D018626:Retroelements; C097504:TGIF1 protein, human