Structural basis for centromere maintenance by Drosophila CENP-A chaperone CAL1

Area of Science:

• Cell Biology
• Molecular Biology
• Epigenetics

Background:

• Centromeres are crucial chromosomal regions for accurate cell division, serving as microtubule attachment sites.
• Centromere identity is maintained by the histone variant CENP-A, which requires specific chaperones for deposition.
• Eukaryotic centromere maintenance mechanisms exhibit plasticity, with differing protein players across species.

Purpose of the Study:

• To elucidate the molecular mechanism by which Drosophila CAL1, a distinct CENP-A chaperone, interacts with CENP-A and CENP-C.
• To understand how CAL1 achieves centromere targeting independently of the Mis18 complex, unlike in humans.

Main Methods:

• X-ray crystallography was employed to determine the structural basis of CAL1 interactions.
• Analysis focused on the binding interfaces between CAL1, CENP-A/H4 nucleosomes, and the CENP-C cupin domain.

Main Results:

• Drosophila CAL1 binds both CENP-A/H4 nucleosomes via its N-terminus and CENP-C via its C-terminus.
• CAL1 binding to CENP-C occurs at the cupin domain dimer interface, independent of the Mis18 complex.
• CAL1 utilizes conserved structural principles for binding CENP-A/H4, despite primary sequence divergence.

Conclusions:

• CAL1 employs a minimalistic mechanism to bind key centromeric components, CENP-A/H4 and CENP-C.
• This study reveals an evolutionarily distinct pathway for centromere maintenance in Drosophila.
• The findings provide critical insights into the conserved and adaptable structural strategies governing centromere identity.