Structure of human spindlin1. Tandem tudor-like domains for cell cycle regulation

Area of Science:

• Structural Biology
• Molecular Biology
• Cancer Research

Background:

• Spindlin1 is a meiotic spindle-binding protein highly expressed in ovarian cancer.
• It is involved in gametogenesis and cell cycle regulation via phosphorylation.
• Its three-dimensional structure and function remain largely uncharacterized.

Purpose of the Study:

• To determine the crystal structure of human spindlin1.
• To elucidate the structural basis for spindlin1's cell cycle regulatory functions.
• To investigate the interaction of spindlin1 with nucleic acids.

Main Methods:

• X-ray crystallography to determine the 2.2Å resolution structure of human spindlin1.
• Site-directed mutagenesis (T95A mutant) to assess the role of phosphorylation.
• Flow cytometry to analyze cell cycle distribution.
• Biochemical assays to identify nucleic acid binding.

Main Results:

• The crystal structure revealed a novel arrangement of tandem Tudor-like domains with three repeats of beta-strands.
• Two phosphate ions were observed, potentially stabilizing a loop involved in cell cycle regulation.
• Spindlin1 expression altered cell cycle distribution in mitosis, while the T95A mutant showed reduced impact.
• Spindlin1 was found to associate with nucleic acids.

Conclusions:

• The determined structure provides the first 3D view of a spin/ssty gene family member.
• Phosphorylation at Thr-95 appears crucial for spindlin1's cell cycle regulatory activity.
• Nucleic acid binding offers a biochemical basis for spindlin1's diverse functions in cell cycle and potentially other processes.