Control of rDNA replication in Tetrahymena involves a cis-acting upstream repeat of a promoter element

Cell. 1986 Oct 24;47(2):229-40. doi: 10.1016/0092-8674(86)90445-9.


A novel genetic scheme was used to isolate mutants altered in the formation or maintenance of amplified rDNA in the Tetrahymena macronucleus. One such mutant had a cis-acting rDNA mutation that affected the ability of mutant rDNA molecules to replicate in macronuclei in the presence of a wild-type (B strain) rDNA. The mutant rDNA was lost from these heterozygous macronuclei during vegetative cell divisions, although it was maintained normally in the homozygous or hemizygous state. In contrast, wild-type macronuclear rDNA of the C3 strain used to obtain the mutant outreplicated B strain rDNA in B/C3 heterozygote macronuclei. Sequence differences were found between wild-type B and C3 and mutant C3 rDNAs in the replication origin region, changing an upstream repeat of a highly conserved rRNA promoter element. We propose that the various rDNA alleles differentially compete for limiting amounts of trans-acting factors that bind to these enhancer-like repeats and positively regulate rDNA replication.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Cell Cycle
  • Cell Nucleus / ultrastructure
  • DNA Replication*
  • DNA, Ribosomal / genetics*
  • Enhancer Elements, Genetic
  • Gene Amplification
  • Gene Expression Regulation
  • Genetic Linkage
  • Mutation
  • Promoter Regions, Genetic*
  • RNA, Ribosomal / genetics*
  • Tetrahymena / genetics*
  • Tetrahymena / ultrastructure


  • DNA, Ribosomal
  • RNA, Ribosomal

Associated data

  • GENBANK/M14749
  • GENBANK/M14751