Structural variation among human beta-tubulin genes.
A chicken beta-tubulin cDNA probe has been used to screen two independently generated human genomic libraries. Of 13 EcoRI fragments detectable in a human genomic Southern blot experiment, 7 correspond in size to EcoRI fragments isolated from recombinant bacteriophage. The location of beta-tubulin-specific regions and the direction of transcription were determined within each cloned fragment. One clone (5 beta) contained a beta-tubulin-specific region of 6.8 kilobase pairs (kbp) that included three intervening sequences as well as a number of inverted repeat structures. The remaining clones contained beta-tubulin-specific sequences that were close to or, in two cases, substantially less than 1.9 kbp long. Because mature human beta-tubulin mRNA is approximately 1.9 kbp long, these short DNA regions cannot on their own encode a functional beta-tubulin mRNA. Analysis using 3'- and 5'-specific probes derived from the chicken cDNA clone showed the presence of both of these end regions within one truncated tubulin-like sequence. A second short tubulin-specific region failed to hybridize with a 3'-specific probe. These short sequences are therefore likely to be examples of pseudogenes that have arisen by loss of a portion of DNA essential to the production of functional human beta-tubulin mRNA.
D000818:Animals; D001483:Base Sequence; D002645:Chickens / Q000235:genetics; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D005796:Genes; D006801:Humans; D008854:Microscopy, Electron; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic; D014404:Tubulin / Q000235:genetics*
D012333:RNA, Messenger; D014404:Tubulin; D004247:DNA