Rfc1 Background Information Yeast origin of replication complex (Orc)1 and Orc2 (also designated Rrr1 or Sir5) bind to autonomously replicating sequences (ARS) and serve as an initiator proteins for DNA replication (1). The minichromosome maintenance (Mcm) proteins bind to chromatin and activate the ORC-ARS complex (2). Cdc6, involved in limiting DNA replication to once per cell cycle, binds to the ORC and is essential for the assembly of the MCM proteins (3). The transcription factor Abf1 (also designated Obf1 or Baf1) also binds to the ARS and plays a role in gene silencing as well as in DNA replication (4). Replication factor C (Rfc)1-5 are required to load the replication clamp proliferating cell nuclear antigen onto primed DNA (5). Sag1-related sequence 2 (Srs2) is a DNA helicase involved in the maintenance of genome integrity and is required for theRad1-dependent removal of long 3' tails (6). Sgs1 is a homologue of the human Bloom's syndrome and Werner's syndrome genes and interacts both physically and genetically with topoisomerase III (7). Myosin-like protein (Mlp)1 and 2 are nuclear envelope associated proteins that form nuclear pore-attached intranuclear filaments (8). Dpb11, an essential BRCT repeat protein, is required for chromosomal DNA replication and the S-phase checkpoint (9).
