Abstract 4296: Cofilin-1 is associated with replicative origins licensing through regulation of MCM2-7 helicase

Abstract

Abstract G1 to S phase transition is strictly regulated to avoid uncontrolled growth in mammalian cells. Although DNA replication initiates in S phase, licensing of DNA replicative origins substantially begins from late M to G1 phase. Interference of replicative origins licensing will lead to genomic instability and cell death. In addition, integral actin organization is required for G1 phase to S phase transition. Whether actin architectures will influence the licensing of DNA replicative origins is unclear. Previously, we found that over-expression of cofilin-1, a member of actin depolymerizing factor (ADF)/cofilin family could destabilize actin cytoskeleton and cause G1 phase arrest. The microarray assay further showed that minichromosome maintenance complex 2-7 (MCM2-7) helicase involved in the establishment of licensing was regulated by cofilin-1. In this study, we aim to investigate whether cofilin-1 would affect the expression of MCM2-7 complexes and the initiation of replicative origins licensing. First, we exploited a double thymidine blockage assay to demonstrate that the cofilin-1 expression was down-regulated during G1 to S phase transition. Use of H1299/tet-on-cofilin-1 cells, we also found that doxycycline induced exogenous cofilin-1 could inhibit the expression of MCM2-7 complex in both dose and time-dependent manners. Chromatin fractionation for analyzing the replicative origin licensing was performed to confirm these observations. DNA fiber analysis for determining the interorigin distance (IOD) was applied to investigate the IOD after the overexpression of cofilin-1 in H1299/tet-on-cofilin-1 cells. Taken together, current results revealed a novel finding that cofilin-1 could regulate MCM2-7 complex for mediating the replicative origin licensing and cell cycle progression. Since MCM2-7 complex has been regarded a prognostic marker of several human cancers, this study may contribute to designing of new therapeutic strategy for cancer treatment. Citation Format: Yi-Jang Lee, Chun-Yuan Chang. Cofilin-1 is associated with replicative origins licensing through regulation of MCM2-7 helicase [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4296.