Figure 8.

Graphical representation of proposed role of SANS in the splicing process. In the nucleus, the USH1G protein SANS controls the tri-snRNP turnover. SANS depletion leads to the accumulation of tri-snRNP intermediates in Cajal bodies and stalls spliceosome assembly at the complex A stage. This can occur due to an imbalance in the recycling of snRNPs components and/or defective release of tri-snRNP complexes from Cajal bodies and their subsequent transfer to nuclear speckles for formation of pre-spliceosomes (complex B). Consistently, cells attempt to compensate low levels of mature tri-snRNP complexes in nuclear speckles by increasing the number of Cajal bodies.