Volume 129, Issue 2, Pages 537-549 (August 2005) Functional Significance and Clinical Phenotype of Nontruncating Mismatch Repair Variants of MLH1  Tiina E. Raevaara, Mari K. Korhonen, Hannes Lohi, Heather Hampel, Elly Lynch, Karin E. Lönnqvist, Elke Holinski-Feder, Christian Sutter, Wendy McKinnon, Sekhar Duraisamy, Anne-Marie Gerdes, Päivi Peltomäki, Maija Kohonen-Ccorish, Elisabeth Mangold, Finlay MacRae, Marc Greenblatt, Albert de la Chapelle, Minna Nyström  Gastroenterology  Volume 129, Issue 2, Pages 537-549 (August 2005) DOI: 10.1053/j.gastro.2005.06.005 Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 1 Schematic representation of the MLH1 protein showing the locations of the studied alterations and known functional domains.14–18 The variants that showed any biochemical defect in the present study are above the diagram, and those with no defects are below the diagram. Gastroenterology 2005 129, 537-549DOI: (10.1053/j.gastro.2005.06.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 2 Expression of MutLα variants in 293T human cells as detected by Western blot analysis. The results were based on at least 3 independent experiments. Twenty variants show low amounts of MLH1 and PMS2 compared with WT proteins (MutLα-WT) in the same lanes. The naturally expressed β-tubulin protein is used as an internal loading control. Gastroenterology 2005 129, 537-549DOI: (10.1053/j.gastro.2005.06.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 3 (A) MMR efficiency of HCT116 nuclear extract (MLH1−/−) complemented with MutLα variants produced in Sf 9 cells. Mock contains heteroduplex DNA with no protein and HCT116 is MMR-deficient extract used as a negative control. The top fragment (3193 base pairs) in each lane shows the migration of the unrepaired linearized G·T mismatch-containing plasmid DNA, and the 2 lower fragments (1833 and 1360 base pairs) indicate repaired and double-digested DNA. (B) Relative repair efficiency (% ratio of double-digested DNA of total DNA added to the reaction): mock, 0%; HCT116 alone, 5% ± 3%; MutLα-WT, 42% ± 6.5%; MutLα-P28L, 2% ± 1%; MutLα-A29S, 45% ± 10%; MutLα-TSI45-47CF, 2% ± 1%; MutLα-D63E, 8% ± 5%; MutLα-G67R, 1% ± 1%; MutLα-del71, 3.5% ± 3%; MutLα-C77R, 1% ± 1%; MutLα-F80V, 6% ± 5%; MutLα-K84E, 1% ± 1%; MutLα-S93G, 58% ± 3%; MutLα-I107R, 1% ± 1%; MutLα-L155R, 7% ± 7%; MutLα-V185G, 8% ± 5%; MutLα-V213M, 39% ± 2.5%; MutLα-I219V, 37% ± 2%; MutLα-S247P, 17% ± 8%; MutLα-H329P, 30% ± 13%; MutLα-del330, 10% ± 10%; MutLα-K443Q, 48% ± 12%; MutLα-L550P, 40.5% ± 2.5%; MutLα-A589D, 41.5% ± 3.5%; MutLα-del612, 32% ± 2%; MutLα-del616, 35% ± 4%; MutLα-K618A, 43.5% ± 7.5%; MutLα-K618T, 45.5% ± 8.5%; MutLα-Y646C, 47% ± 7%; MutLα-P648L, 43% ± 2%; MutLα-P648S, 53% ± 7%; MutLα-P654L, 46.5% ± 6.5%; MutLα-R659P, 19.5% ± 9%; MutLα-R659Q, 36% ± 3%; MutLα-A681T, 48.5% ± 6.5%; MutLα-V716M, 46% ± 7.5%, MutLα-del633-663, 1% ± 1% (not shown). Values are mean ± SD of 3–10 independent experiments. Gastroenterology 2005 129, 537-549DOI: (10.1053/j.gastro.2005.06.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 4 Subcellular localization of MLH1-EGFP and PMS2-EGFP fusion proteins detected by direct fluorescence analysis. The same nuclei are also shown with 4′,6-diamidino-2-phenylindole staining. (A) (Left) Nuclear expression of MLH1-EGFP WT without PMS2. (Right) Coexpression with PMS2, completely imported into the nucleus. (B) (Left) Cytoplasmic expression of PMS2-EGFP without MLH1. (Right) Coexpression with MLH1 increases nuclear proportion. (C) (Left) Nuclear expression of MLH1-EGFP A29S mutation similar to WT MLH1. (Middle) Nuclear expression of MLH1-EGFP A29S with and without PMS2. (Right) Coexpression with MLH1; also, PMS2-EGFP is transferred into the nucleus. (D) Amino-terminal mutant MLH1-EGFP D63E hinders nuclear localization of both MLH1 and PMS2. (Left) Cytoplasmic expression of MLH1-EGFP D63E construct. (Middle) Cytoplasmic expression of complex with PMS2. (Right) Mainly cytoplasmic expression of D63E-PMS2 complex. (E) Carboxyl-terminal mutation MLH1-EGFP L550P hinders the nuclear import of PMS2. (Left) Nuclear expression of MLH1-EGFP L550P construct. (Middle) Nuclear expression of complex with PMS2. (Right) Cytoplasmic coexpression of PMS2-EGFP and MLH1 L550P. (Original magnification 630×.) Gastroenterology 2005 129, 537-549DOI: (10.1053/j.gastro.2005.06.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions