Activation of a dormant replication origin is essential for Haloferax mediterranei lacking the primary origins

Haibo Yang,Lei Wang,Xiaoqing Liu,Hua Xiang,Zhenfang Wu,Shuangfeng Cai,Jingfang Liu

doi:10.1038/ncomms9321

Abstract

The use of multiple origins for chromosome replication has been demonstrated in archaea. Similar to the dormant origins in eukaryotes, some potential origins in archaea appear to be inactive during genome replication. We have comprehensively explored the origin utilization in Haloferax mediterranei. Here we report three active chromosomal origins by genome-wide replication profiling, and demonstrate that when these three origins are deleted, a dormant origin becomes activated. Notably, this dormant origin cannot be further deleted when the other origins are already absent and vice versa. Interestingly, a potential origin that appears to stay dormant in its native host H. volcanii lacking the main active origins becomes activated and competent for replication of the entire chromosome when integrated into the chromosome of origin-deleted H. mediterranei. These results indicate that origin-dependent replication is strictly required for H. mediterranei and that dormant replication origins in archaea can be activated if needed.

Highlights

The use of multiple origins for chromosome replication has been demonstrated in archaea
When oriC4-cdc6H was replaced with oriP2-orc[13], a putative dormant origin from H. volcanii, oriP2-orc[13] could efficiently initiate the replication of the entire chromosome of H. mediterranei in the absence of all other active origins. These results demonstrate that dormant origins can be activated in archaea if needed, and that chromosome replication in H. mediterranei, unlike that in H. volcanii, strictly requires origin-dependent initiation
Because replication origins are dependent on adjacent initiator proteins (Cdc6) for firing[10,21], the replication origins of the H. mediterranei chromosome were predicted using Cdc[6] and potential origin recognition boxes (ORBs) associated with these initiator genes[12]

Summary

Introduction

The use of multiple origins for chromosome replication has been demonstrated in archaea. A potential origin that appears to stay dormant in its native host H. volcanii lacking the main active origins becomes activated and competent for replication of the entire chromosome when integrated into the chromosome of origin-deleted H. mediterranei. When oriC4-cdc6H was replaced with oriP2-orc[13], a putative dormant origin from H. volcanii, oriP2-orc[13] could efficiently initiate the replication of the entire chromosome of H. mediterranei in the absence of all other active origins. These results demonstrate that dormant origins can be activated in archaea if needed, and that chromosome replication in H. mediterranei, unlike that in H. volcanii, strictly requires origin-dependent initiation

Methods

Results

Conclusion