Human Cdc45 is a proliferation‐associated antigen

Abstract

Cell division cycle protein 45 (Cdc45) plays a critical role in DNA replication to ensure that chromosomal DNA is replicated only once per cell cycle. We analysed the expression of human Cdc45 in proliferating and nonproliferating cells. Our findings show that Cdc45 protein is absent from long‐term quiescent, terminally differentiated and senescent human cells, although it is present throughout the cell cycle of proliferating cells. Moreover, Cdc45 is much less abundant than the minichromosome maintenance (Mcm) proteins in human cells, supporting the concept that origin binding of Cdc45 is rate limiting for replication initiation. We also show that the Cdc45 protein level is consistently higher in human cancer‐derived cells compared with primary human cells. Consequently, tumour tissue is preferentially stained using Cdc45‐specific antibodies. Thus, Cdc45 expression is tightly associated with proliferating cell populations and Cdc45 seems to be a promising candidate for a novel proliferation marker in cancer cell biology.

Cdc45 Limits Replicon Usage from a Low Density of preRCs in Mammalian Cells

“…In contrast, and unlike the embryonic situation, somatic cells have very low levels of Cdc45 even though this is an upper estimate. This is in agreement with another study that found Cdc45 to reside at low levels in human tumor cells [38].…”

Cell Cycle-Dependent Mobility of Cdc45 Determined in vivo by Fluorescence Correlation Spectroscopy

“…With a nuclear volume of about 500 to 600 fl for the HeLa S3 cells [24] this would yield 10,000 to 20,000 molecules of eGFP-Cdc45 per cell. Our quantitative western blot experiments shown in Figure 1b revealed that the ratio of eGFP-Cdc45 to endogenous Cdc45 is approximately 1 to 4 resulting in an estimate endogenous Cdc45 number of 40,000 to 80,000 molecules per cell, which is in agreement with previous estimated numbers of Cdc45 molecules per cell being 45,000 [28].…”

“…Antibodies recognizing Cdc45 (C45-3G10-111) [4], p125 of Pol δ (PGD-5E1) [28] and RPA 32 (RBF-4E4) [36], [37]. Anti-Mcm5 antibody was obtained from Prof R. Knippers [38].…”

Structural and Functional Insights into the DNA Replication Factor Cdc45 Reveal an Evolutionary Relationship to the DHH Family of Phosphoesterases

“…As many other DNA replication factors, Cdc45 is more abundant in proliferating cells, whereas it is almost absent from long term quiescent, terminally differentiated, and senescent cells (8). Several genetic studies, two-hybrid screens, and co-immunoprecipitation analyses revealed that Cdc45 interacts with a number of other replication factors, including the Mcm2-7 complex, GINS, MCM10, replication protein A, DNA polymerases ␣, ␦, and ⑀, the origin recognition complex subunit 2, and TopBP1 (for a review see Ref.…”