Beta-tubulin mRNA Research Articles

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.

Multiple alpha and beta tubulin genes represent unlinked and dispersed gene families.

Cloned cDNA sequences specific for alpha or beta tubulin mRNAs have been used to show that the multigene families which encode either alpha or beta tubulin are unlinked and dispersed throughout the chicken genome. Fractions of chicken chromosomes partially purified by centrifugation on a sucrose gradient were digested with restriction endonucleases and electrophoresed on agarose gels. The DNA was transferred to nitrocellulose filters and hybridized to labeled probes constructed from cloned cDNA sequences specific for alpha or beta tubulin. We find alpha tubulin sequences on four different chicken chromosomes and beta tubulin sequences on at least two different chromosomes. Moreover, using chicken chromosomes further purified with a fluorescent cell sorter, we have been able unambiguously to localize alpha tubulin genes to chromosome 1 and chromosome 8 and two of the beta genes to chromosome 2.

RNA synthesis in starved deciliated Tetrahymena pyriformis.

Tetrahymena pyriformis which has been starved for 20 h by incubation in buffer, and then deciliated, can regenerate its cilia in about 90 min while still in suspension in non-nutrient medium. The process of reciliation is accompanied by protein synthesis which begins a few minutes after deciliation and by synthesis of ribosomal and messenger RNAs during a period extending from about 1 h to about 3 h after deciliation. Although net synthesis of RNA remains at a very low level until 1 h after deciliation, a qualitative change in the translatable poly(A)-containing messenger RNA content of deciliated cells, and in particular, formation of beta-tubulin mRNA can be detected almost immediately after deciliation.