Genetic modulation of RNA metabolism in Drosophila [melanogaster]. III. Requirement for an rDNA-deficient X chromosome in YbbSuVar-5-mediated increases in RNA synthesis

• Published in: Genetics (Austin) 1979-10, Vol.93 (2), p.411-422
• Main Authors: Strausbaugh, Linda D, Kiefer, Barry I
• Format: Article
• Language: English
• Subjects: Investigations
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/93.2.411

Males of the genotype car bb/YbbSuVar-5 have an approximately two-fold increase in the rate of accumulation of 4S, 5S, 18s + 28s and poly-A+ RNA molecules when compared to males of the genotype car bb/Ybb- (CLARK, STRAUSBAUGH and KIEFER 1977; CLARK and KIEFER 1977). Experiments were designed to determine if the modulation of RNA metabolism by YbbSuVar-5 requires an rDNA deficiency on the X chromosome. Synthetic rates for 4S, 5S, and 18s + 28s RNA's were measured in the genotypes Sam+iso/Ybb- and Sam+iso/Ybbsuvar-5 by injecting adult males with 3H-uridine, allowing them to incorporate label for two hours, fractionating extracted RNA by polyacrylamide gel electrophoresis and determining the specific activities of RNA's (dpm/μgRNA). The results of these determinations showed that the synthetic rates for 4S, 5S, and 18s + 28S RNA's are the same in these two genotypes, demonstrating that the YbbSuVar-5 chromosome does not increase transcription when paired with an X chromosome that is wild type for rDNA. Saturation hybridization was used to measure the rDNA content in several genotypes. These results showed that Sam+iso/YbbSuVar-5 males and Sam+iso/Ybb- males have equivalent amounts of rDNA.—These results are consistent with the suggestion that the Ybb- and YbbSuVar-5 chromosomes have similar amounts of rDNA. The nature of compensatory strategies in rDNA-deficient genotypes is discussed.