Transaldolase (TAL) is a key enzyme of the pentose phosphate pathway, which is responsible for generation of reducing equivalents to protect cellular integrity from reactive oxygen intermediates. While exons 2 and 3 are highly repetitive, the complete TAL-H gene is mapped to a single genomic locus (TALDO12) by several independent approaches. Southern blot hybridization of a 827-bp 3' EcoRI fragment of the TAL-H cDNA to human-mouse somatic cell hybrid DNA localized TALDO1 to the p13 → pter region of chromosome 11. Fluorescence in situ hybridization with a 15-kb genomic fragment harboring exons 1 and 2 mapped TALDO1 to 11p15.4-p15.5. A truncated and mutated segment of TAL-H exon 5 terminating with a poly(A) tail was identified in a pseudogene locus (TALDOP1) on chromosome 1. Reverse transcriptase-PCR studies of human-mouse somatic cell hybrids revealed the presence of the functional TAL-H gene on chromosome 11 and its absence on human chromosome 1. Mapping of radiation hybrids placed TALDO1 between markers WI-1421 and D11S922 on 11p15.
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