Fig. 7: Trim37 promotes the stability of Bcl6 and differentiation of T_FH cell dependent on the MATH domain.

a Schematic presentation of full-length Trim37 and its mutants. RING, ring-finger domain; Bbox, B-box domain; CC, coiled-coil domain; MATH, meprin and TRAF–C homology domain. b Immunoblot analysis of lysates obtained from the HEK293T cells transfected with Flag-tagged Bcl6 and HA-tagged full-length Trim37 or Trim37 mutants as indicated, followed by immunoprecipitation with anti-Flag affinity gel and immunoblot analysis with anti-HA or anti-Flag Abs. c Immunoblot analysis of lysates obtained from the HEK293T cells transfected with Flag-tagged Bcl6, His-tagged ubiquitin, and the HA-tagged vectors Trim37^WT, Trim37^△MATH, Trim37^G322V. This process was followed by immunoprecipitation with an anti-Flag affinity gel and analysis with anti-HA, anti-Flag, and anti-His Abs. d Immunoblot analysis of Bcl6 in lysates of the HEK293T cells transfected with HA-tagged Bcl6 and empty vector, Trim37^WT, Trim37^△MATH, and Trim37^G322V. Then, the cells were treated with CHX for the indicated hours. Residual Bcl6 protein was normalized to actin and presented relative to that before the addition of CHX (right). e, f WT and Trim37^G322V/G322V bone marrow chimeric mice were infected with the influenza virus for 10 days, and the spleens were collected for FACS analysis. e Representative flow cytometry plots showing the frequency of CD45.1⁺ (WT, n = 4) or CD45.2⁺ (Trim37^G322V/G322V, n = 4) CXCR5⁺PD1⁺ T_FH cells as a percentage of CD4⁺ T cells in the spleen. f Representative flow cytometry plots showing the frequency of CD45.1⁺ (WT, n = 4) or CD45.2⁺ (Trim37^G322V/G322V, n = 4) CXCR5⁺Bcl6⁺ T_FH cells as a percentage of CD4⁺Foxp3^- T cells in the spleen. g Schematic model for the Trim37-mediated ubiquitination of Bcl6 and regulation of T_FH cell differentiation. Data are representative of two (e, f) or at least three (a–d) independent experiments, and were analyzed by two-tailed paired Student’s t-test (e, f). Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ns, not significant.