Interactions between telomerase and primase physically link the telomere and chromosome replication machinery.
In the ciliate Euplotes crassus, millions of new telomeres are synthesized by telomerase and polymerase alpha-primase during macronuclear development in mated cells. Concomitant with de novo telomere formation, telomerase assembles into higher-order complexes of 550 kDa, 1,600 kDa, and 5 MDa. We show here that telomerase is physically associated with the lagging-strand replication machinery in these complexes. Antibodies against DNA primase precipitated telomerase activity from all three complexes from mated cells but not the 280-kDa telomerase complex from vegetatively growing cells. Moreover, when telomerase was affinity purified, primase copurified with enzyme from mated cells but not with the 280-kDa vegetative complex. Thus, the association of telomerase and primase is developmentally regulated. Intriguingly, PCNA (proliferating cell nuclear antigen) was also found in the 5-MDa complex from mated cells. We therefore speculate that this complex is a complete telomere synthesis machine, while the smaller complexes are assembly intermediates. The physical association of telomerase and primase explains the coordinate regulation of telomeric G- and C-strand synthesis and the efficiency of telomere addition in E. crassus.
Department of Pediatrics, University of California, San Diego School of Medicine, La Jolla, California 92093-0627, USA.
Saugata
S
Ray
Zemfira
Z
Karamysheva
Libin
L
Wang
Dorothy E
DE
Shippen
Carolyn M
CM
Price
D000818:Animals; D002875:Chromosomes / Q000378:metabolism*; D019915:DNA Primase / Q000737:chemistry / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology*; D016812:Euplotes / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D046911:Macromolecular Substances; D008970:Molecular Weight; D011233:Precipitin Tests; D021122:Protein Subunits; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D019098:Telomerase / Q000737:chemistry / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism*
D046911:Macromolecular Substances; D021122:Protein Subunits; D015800:Protozoan Proteins; D019915:DNA Primase; D019098:Telomerase