Galej Group

Structure and function of RNA-protein complexes

The Galej group uses an integrated structural biology approach combined with biochemistry and biophysics to investigate large RNA-protein complexes involved in gene expression.


Previous and current research

In eukaryotes, genetic information in protein-coding genes is dispersed in the form of short fragments (exons), which are punctuated with non-coding segments known as introns. Introns are removed from precursors of messenger RNAs (pre-mRNA) in a reaction catalysed by a multi-megadalton RNA–protein complex – the spliceosome. More than 100 proteins and five small nuclear RNAs (snRNAs) are involved in orchestrating this process. Among them, five small nuclear ribonucleoprotein particles (U1, U2, U4/U6, and U5 snRNPs) are the major building blocks of the splicing machinery. Recent technological advances in cryo-electron microscopy (cryo-EM) have allowed determination of high-resolution structures for nearly all yeast spliceosome assembly intermediates, providing unprecedented mechanistic insights into spliceosome assembly, activation, and catalysis.

Our group investigates three major problems related to the pre-mRNA splicing:

  1. U12-dependent splicing in mammalian cells.
  2. Biogenesis of snRNPs, the building blocks of the spliceosome.
  3. snRNA processing in metazoans by the Integrator complex.

In human cells, most introns are processed by the canonical U2-dependent, major spliceosome. However, around 0.5% of human introns utilise an alternative splicing pathway, catalysed by the minor spliceosome, which depends on the U12 snRNA. While U12-dependent introns are rare, they are often located in genes with critical cellular functions, and mutations in the minor spliceosome components lead to several genetic disorders.

By combining cell-based assays, proteomics, and next-generation sequencing methods, we aim to obtain a comprehensive picture of the minor spliceosome composition and associated regulatory mechanisms.

The core of our expertise lies in structural studies by single-particle cryo-EM. We expect that high-resolution structural information for the minor spliceosome will answer some of the fundamental mechanistic questions regarding its assembly and U12-dependent intron recognition. Additionally, it will shed light on structural similarities and differences between the major and minor splicing pathways, and will provide insights into the evolution of the splicing machinery. 

Research in our laboratory combines biochemical approaches, proteomics, and cell biology with high-resolution cryo-EM to study the structure and function of large macromolecular assemblies.

Future projects

  • Structural and functional characterisation of the U12-dependent spliceosome assembly intermediates.
Figure 1: Structure of the 44-subunit catalytic step 1 spliceosome determined by cryo-EM to 3.8 Å resolution (Galej et al., Nature, 2016).
Figure 2: Schematics of the U2- and U12-dependent splicing pathways in mammalian cells.
Figure 2: Schematics of the U2- and U12-dependent splicing pathways in mammalian cells.