Amplification of tandemly repeated origin control sequences confers a replication advantage on rDNA replicons in Tetrahymena thermophila.
Mol Cell Biol
; 10(5): 2070-80, 1990 May.
Article
in En
| MEDLINE
| ID: mdl-2325646
ABSTRACT
The macronuclear rRNA genes (rDNA) in the ciliate Tetrahymena thermophila are normally palindromic linear replicons, containing two copies of the replication origin region in inverted orientation. A circular plasmid containing a single Tetrahymena rRNA gene (one half palindrome) joined to a tandem repeat of a 1.9-kilobase (kb) rDNA segment encompassing the rDNA replication origin and known replication control elements was used to transform Tetrahymena macronuclei by microinjection. This plasmid was shown previously to have a replication advantage over the rDNA allele of the recipient cell strain (G.-L. Yu and E. H. Blackburn, Proc. Natl. Acad. Sci. USA 868487-8491, 1990). During vegetative cell divisions, the circular and palindromic rDNAs were rapidly replaced by novel, successively longer linear rDNAs that eventually contained up to 30 tandem 1.9-kb repeats, resulting from homologous but unequal crossovers between the 1.9-kb repeats. We present evidence to show that increasing the number of copies of the replication control regions increases the replicative advantage of the rDNA, the first such situation for a cellular nuclear replicon in a eucaryote.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Replicon
/
Tetrahymena
/
DNA, Ribosomal
/
Regulatory Sequences, Nucleic Acid
/
Gene Amplification
Limits:
Animals
Language:
En
Journal:
Mol Cell Biol
Year:
1990
Type:
Article