Fig. 8: Hom2 and Hom4 regions are important for TSSC4 function in tri-snRNP formation.

a TSSC4 was downregulated by siRNA followed by expression of siRNA-resistant WT TSSC4-GFP, ΔHom2-GFP, ΔHom4-GFP, and Hom4-2_Ala-GFP constructs. Tri-snRNP formation was assayed by U5 snRNA localization (turquoise) in Cajal bodies visualized by immunodetection of their marker coilin (red). U5 snRNA localization in Cajal bodies is increased when tri-snRNP assembly is inhibited. Cajal bodies marked by arrows are enlarged five times in insets. Scale bar represents 10 μm. b Quantification of U5 snRNA Cajal body accumulation. In situ hybridization signal in the Cajal body was normalized to the average signal in the nucleoplasm. In total, 41–50 cells were assayed (see bottom of the diagram for the precise number of assayed cells) and results are shown as a box blot (center line—median; box limits—1st and 3rd quartiles; whiskers—5th and 95th percentile). Two lowest and two highest values are depicted as separate dots in each box plot. Statistical significance was determined by the two-tailed T test. *** indicates P ≤ 0.001; **** indicates P ≤ 0.0001. Original values for box plots are provided in the Source Data file. See also Supplementary Fig. 5 for correlation between TSSC4-GFP expression and U5 snRNA Cajal body accumulation. c A model of TSSC4 function in U5 snRNP metabolism.