Capturing novel mouse genes encoding chromosomal and other nuclear proteins

Area of Science:

• Cell Biology
• Genetics
• Molecular Biology

Background:

• Vast gene sequences exist, but gene functions remain largely unknown.
• Determining protein sub-cellular localization is a key strategy for assigning gene function.
• The nucleus contains numerous compartments with poorly understood protein compositions.

Purpose of the Study:

• To identify mouse genes encoding proteins localized to specific nuclear compartments.
• To characterize novel nuclear proteins and their functions.
• To explore potential links between identified proteins and cellular regulatory mechanisms.

Main Methods:

• Utilized a gene trap approach by splicing endogenous gene sequences to a promoterless betageo reporter in mouse embryonic stem (ES) cells.
• Screened ES cell lines for betageo fusions localized to sub-nuclear compartments like chromosomes, nucleolus, and splicing factor foci.
• Determined the sequences of 11 trapped genes and validated protein localization for two genes.

Main Results:

• Successfully identified 11 trapped genes encoding proteins with specific sub-nuclear localizations.
• Discovered three novel proteins localized to distinct chromosomal domains, including a putative serine/threonine kinase.
• Identified a gene product co-localizing with spliceosome components, suggesting a role as an E3 ubiquitin-protein ligase.
• The majority of isolated genes represent novel, uncharacterized genes.

Conclusions:

• The gene trap approach is effective for identifying genes with novel proteins and specific nuclear localizations.
• The study highlights significant gaps in our understanding of the nucleus's protein content.
• Identified protein motifs suggest new connections between ubiquitination, phosphorylation, mRNA splicing, and chromosome biology.