DNA replication depends critically upon chromatin structure. Little is known 
about how the replication complex overcomes the nucleosome packages in chromatin 
during DNA replication. To address this question, we investigate factors that 
interact in vivo with the principal initiation DNA polymerase, DNA polymerase 
alpha (Polalpha). The catalytic subunit of budding yeast Polalpha (Pol1p) has 
been shown to associate in vitro with the Spt16p-Pob3p complex, a component of 
the nucleosome reorganization system required for both replication and 
transcription, and with a sister chromatid cohesion factor, Ctf4p. Here, we show 
that an N-terminal region of Polalpha (Pol1p) that is evolutionarily conserved 
among different species interacts with Spt16p-Pob3p and Ctf4p in vivo. A 
mutation in a glycine residue in this N-terminal region of POL1 compromises the 
ability of Pol1p to associate with Spt16p and alters the temporal ordered 
association of Ctf4p with Pol1p. The compromised association between the 
chromatin-reorganizing factor Spt16p and the initiating DNA polymerase Pol1p 
delays the Pol1p assembling onto and disassembling from the late-replicating 
origins and causes a slowdown of S-phase progression. Our results thus suggest 
that a coordinated temporal and spatial interplay between the conserved 
N-terminal region of the Polalpha protein and factors that are involved in 
reorganization of nucleosomes and promoting establishment of sister chromatin 
cohesion is required to facilitate S-phase progression.