Developmentally controlled telomere addition in wild-type and mutant paramecia.
We analyzed sites of macronuclear telomere addition at a single genetic locus in Paramecium tetraurelia. We showed that in homozygous wild-type cells, differential genomic processing during macronuclear development resulted in the A surface antigen gene being located 8, 13, or 26 kilobases upstream from a macronuclear telomere. We describe variable rearrangements that occurred at the telomere 8 kilobases from the A gene. A mutant (d48) that forms a telomere near the 5' end of the A gene was also analyzed. This mutant was shown to create simple terminal deletions; telomeric repeats were added directly to the truncated wild-type A gene sequence. In both the mutant and wild-type cells, the telomeric sequences (a mixture of C4A2 and C3A3 repeats) were added to various sequences within a specific 200- to 500-base-pair region rather than to a single site. No similarities were found in the primary sequences surrounding the telomere addition sites. The mutation in d48 changed the region of telomere addition at the A gene locus; this is the first example in ciliates of a mutation that affects the site of telomere addition.
Forney
J D
JD
Department of Molecular Biology, University of California, Berkeley 94720.
Blackburn
E H
EH
D000818:Animals; D000954:Antigens, Surface / Q000235:genetics; D001483:Base Sequence; D002872:Chromosome Deletion; D002875:Chromosomes / Q000648:ultrastructure*; D004247:DNA / Q000235:genetics; D005796:Genes; D008040:Genetic Linkage; D008969:Molecular Sequence Data; D009154:Mutation; D010247:Paramecium / Q000235:genetics*
D000954:Antigens, Surface; D004247:DNA