Structure of the human GINS complex and its assembly and functional interface in replication initiation

Abstract

The eukaryotic GINS complex is essential for the establishment of DNA replication forks and replisome progression. We report the crystal structure of the human GINS complex. The heterotetrameric complex adopts a pseudo symmetrical layered structure comprising two heterodimers, creating four subunit-subunit interfaces. The subunit structures of the heterodimers consist of two alternating domains. The C-terminal domains of the Sld5 and Psf1 subunits are connected by linker regions to the core complex, and the C-terminal domain of Sld5 is important for core complex assembly. In contrast, the C-terminal domain of Psf1 does not contribute to the stability of the complex but is crucial for chromatin binding and replication activity. These data suggest that the core complex ensures a stable platform for the C-terminal domain of Psf1 to act as a key interaction interface for other proteins in the replication-initiation process.

Crystal structure of the GINS complex and functional insights into its role in DNA replication

“…Around the ␤-sheet are two helices and a ␤-hairpin or loop, forming a small but definable ␤-domain in these three subunits. The monomeric structures overlap well with the reported GINS structure (13), especially within the ␣-domains. However, conformational differences are noted in the ␤-domains of each subunit (Fig.…”

“…The body of the tetramer is composed of ␣-helices with few peripheral short ␤-strands. The gross structural features are essentially the same as those recently reported for the structure containing a truncated Psf1 subunit (13); in the reported structure, 47 residues of the C-terminal region of Psf1 had to be deleted for crystallization. Surprisingly, even though we crystallized GINS with all fulllength proteins, only the first 145 residues of Psf1 were ordered.…”

“…This complex included the full-length proteins of each of the four subunits. During the preparation of this work, the structure of the human GINS complex containing a truncated Psf1 subunit appeared (13). The tetramer structure that we have obtained is basically the same as that reported by Kamada et al (13); the folds of each subunit and the interactions between the four subunits are essentially the same with slight variations found for certain loops and ␤-strands.…”

“…Surprisingly, even though we crystallized GINS with all fulllength proteins, only the first 145 residues of Psf1 were ordered. These residues were present in the structure containing truncated Psf1 reported by Kamada et al (13). The C-terminal 51 residues of Psf1 are not visible in our structure, indicating that this region is intrinsically disordered.…”

“…Kamada et al (13) reported that their GINS complex crystallized only when a Psf1 mutant lacking the C-terminal 47 residues (14) was used, suggesting that the presence of this ␤-domain inhibited crystal packing of the GINS complex. Kamada et al (13) proposed that the deleted region of Psf1 folds into a ␤-domain structure and that the correct positioning of this domain on the surface of the GINS complex is critical for function. However, we crystallized the GINS complex with all full-length proteins under different crystallization conditions but in the same space group with similar unit cell dimensions.…”