Initiation, Elongation, and Termination of Replication in Eukaryotes

Many of the proteins and enzymes involved in initiation at replication origins and DNA chain growth at replication forks have the same biochemical activities as their counterparts in bacteria. However, the situation regarding terminators and terminator proteins is less clear. Whether they exist to delineate to any extent individual replicons or clusters of replicons is not known. In the case of eukaryotic chromosomes, however, there is a special mechanism to replicate their ends which are known as telomeres. 

Question What are the structural features of origins of replication in eukaryotes and how is initiation 

Most progress in understanding this has been made in the yeast Saccharomyces cerevisiae from the chromosomes of which sequences have been identified that allow initiation of replication when inserted into plasmids (see below). These sequences are called autonomously replicating sequences (ARSs). It is likely that some of them, at least, represent bona fide replication origins. Presumably the mechanism of initiation at these origins is similar to that which has been elucidated in bacteria. 

Question What is known about the process of DNA chain growth at replication forks in eukaryotes  

The structure of replication forks in eukaryotes is essentially the same as in bacteria. Chain growth is continuous on the leading strand and discontinuous on the lagging strand. There are equivalents of the polymerases, helicase, primase, SSB, etc., but there are clearly some differences. For example, two different polymerases, DNA polymerase 8 and DNA polymerase a, function on the leading and lagging strand, respectively. Also, the mitochondrion has its own DNA polymerase. 

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