TP53 Mutations Are Associated with Increased Infections and Reduced Hematopoietic Cell Transplantation Rates in Myelodysplastic Syndrome and Acute Myeloid Leukemia.

Although allogeneic hematopoietic cell transplantation (HCT) is the sole potentially curative therapy for patients with poor-risk myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), only a minority of these patients undergo HCT. Patients with TP53-mutated (TP53MUT) MDS/AML are at particularly high risk, yet fewer TP53MUT patients undergo HCT compared with poor-risk TP53-wild type (TP53WT) patients. We hypothesized that TP53MUT MDS/AML patients have unique risk factors affecting the rate of HCT and thus investigated phenotypic changes that may prevent patients with TP53MUT MDS/AML from receiving HCT. In this single-center retrospective analysis of outcomes for adults with newly diagnosed MDS or AML (n = 352), HLA typing was used as a surrogate for physician "intent to transplant." Multivariable logistic regression models were used to estimate odds ratios (ORs) for factors associated with HLA typing, HCT, and pretransplantation infections. Multivariable Cox proportional hazards models were used to create predicted survival curves for patients with and those without TP53 mutations. Overall, significantly fewer TP53MUT patients underwent HCT compared to TP53WT patients (19% versus 31%; P = .028). Development of infection was significantly associated with decreased odds of HCT (OR, .42; 95% CI, .19 to .90) and worse overall survival (hazard ratio, 1.46; 95% CI, 1.09 to 1.96) in multivariable analyses. TP53MUT disease was independently associated with increased odds of developing an infection (OR, 2.18; 95% CI, 1.21 to 3.93), bacterial pneumonia (OR, 1.83; 95% CI, 1.00 to 3.33), and invasive fungal infection (OR, 2.64; 95% CI, 1.34 to 5.22) prior to HCT. Infections were the cause of death in significantly more patients with TP53MUT disease (38% versus 19%; P = .005). With substantially more infections and decreased HCT rates in patients with TP53 mutations, this raises the possibility that phenotypic changes occurring in TP53MUT disease may affect infection susceptibility in this population and drastically impact clinical outcomes.

Diverse sequences are functional at the C-terminus of the E. coli periplasmic chaperone SurA.

SurA is a major periplasmic molecular chaperone in Escherichia coli and has been shown to assist the biogenesis of several outer membrane proteins. The C-terminal fragment of SurA folds into a short ß-strand, which forms a small three-stranded anti-parallel ß-sheet module with the N-terminal ß-hairpin. We found that the length of the C-terminal fragment, rather than its exact amino acid composition, had a big impact on SurA function. To investigate the determinant factor of the C-terminal sequence, we created a library of SurA constructs randomized in the last 10 residues. We screened the library and randomly analyzed 19 constructs that displayed SurA activity. The C-termini of these constructs shared little sequence similarity, except that ß-strand-forming residues were preferentially enriched. Three SurA constructs were expressed and purified for structural characterization. Circular dichroism and fluorescence spectroscopy analyses revealed that their structures were similar to the structure of the wild-type SurA. Our results suggest that for scaffolding purpose proteins may tolerate various sequences provided certain general requirements such as hydrophobicity and secondary structure propensity are satisfied. Furthermore, the sequence tolerance of SurA at the C-terminus indicates that this area is not likely to be involved in substrate binding.

Insights into the function and structural flexibility of the periplasmic molecular chaperone SurA.

SurA is the primary periplasmic molecular chaperone that facilitates the folding and assembling of outer membrane proteins (OMPs) in Gram-negative bacteria. Deletion of the surA gene in Escherichia coli leads to a decrease in outer membrane density and an increase in bacterial drug susceptibility. Here, we conducted mutational studies on SurA to identify residues that are critical for function. One mutant, SurA(V37G), significantly reduced the activity of SurA. Further characterization indicated that SurA(V37G) was structurally similar to, but less stable than, the wild-type protein. The loss of activity in SurA(V37G) could be restored through the introduction of a pair of Cys residues and the subsequent formation of a disulfide bond. Inspired by this success, we created three additional SurA constructs, each containing a disulfide bond at different regions of the protein between two rigid secondary structural elements. The formation of disulfide bond in these mutants has no observable detrimental effect on protein activity, indicating that SurA does not undergo large-scale conformational change while performing its function.