Research involving the cold shock gene cspA of the medically important bacterium Staphylococcus aureus is steadily increasing as the relationships between the activity of this gene at 37 °C and a spectrum of virulence factors (e.g., biofilm formation, capsule production) as well as stress-related genes (e.g., alkaline shock protein, asp-23 and the alternative sigma factor, sigB) are distinguished. Fundamental to each of these discoveries is defining the regulation of cspA and the production of its protein product CspA. In this paper, primer extension analysis was used to identify a transcriptional start point at 112 bp upstream of the initiation codon of the cspA coding sequence from S. aureus Newman RNA collected at 37 °C. Based on the location of the putative −10 and −35 sites as well as putative cold shock protein binding sites, a 192 bp sequence containing an 80 bp promoter + a 112 bp 5′ UTR was generated by polymerase chain reaction. The activity of this 192 bp sequence was confirmed in a pLL38 promoter::xylE reporter gene construct. In addition, Western blots were used to confirm the production of CspA at 37 °C and demonstrated that production of the protein was not constitutive but showed growth-dependent production with a significant increase at the 6 h time point. The results presented identify another regulatory region for the cold shock gene cspA of S. aureus and show growth-dependent activity of both this cspA regulatory sequence, presented as a 192 bp sequence of promoter + 5′ UTR and the production of the CspA protein at 37 °C. The presence of two active transcription start points, a −112 bp sequence defined in this work and a second previously defined at −514 bp upstream of the cspA initiation codon, suggests the possibility of interactions between these two regions in the regulation of cspA. The growth-dependent production of the cold shock protein CspA supports the availability of this protein to be a modulator of virulence and stress factor genes at 37 °C.

The coordination of zinc by histone deacetylase inhibitors (HDACi), altering the bioavailability of zinc to histone deacetylases (HDACs), is key to HDAC enzyme inhibition. However, the ability of zinc binding groups (ZBGs) to alter intracellular free Zn⁺² levels, which may have far-reaching effects, has not been explored. Using two HDACis with different ZBGs, we documented shifts in intracellular free Zn⁺² concentrations that correlate with subsequent ROS production. Next, we assayed refolding and reactivation of the R175H mutant p53 protein in vitro to provide greater biological context as the activity of this mutant depends on cellular zinc concentration. The data presented demonstrates the differential activity of HDACi in promoting R175H response element (RE) binding. After cells are treated with HDACi, there are differences in R175H mutant p53 refolding and reactivation, which may be related to treatments. Collectively, we show that HDACis with distinct ZBGs differentially impact the intracellular free Zn⁺² concentration, ROS levels, and activity of R175H; therefore, HDACis may have significant activity independent of their ability to alter acetylation levels. Our results suggest a framework for reevaluating the role of zinc in the variable or off-target effects of HDACi, suggesting that the ZBGs of HDAC inhibitors may provide bioavailable zinc without the toxicity associated with zinc metallochaperones such as ZMC1.

While most cases of cutaneous squamous cell carcinoma (cSCC) are benign, invasive cSCC is associated with higher mortality and is often more difficult to treat. As such, understanding the factors that influence the progression of cSCC are important. Aggressive cancers metastasize through a series of evolutionary changes, collectively called the epithelial-to-mesenchymal transition (EMT). During EMT, epithelial cells transition to a highly mobile mesenchymal cell type with metastatic capacities. While changes in expression of TGF-β, ZEB1, SNAI1, MMPs, vimentin, and E-cadherin are hallmarks of an EMT process occurring within cancer cells, including cSCC cells, EMT within tissues is not an “all or none” process. Using patient-derived cSCC and adjacent normal tissues, we show that cells within individual cSCC tumors are undergoing a hybrid EMT process, where there is variation in expression of EMT markers by cells within a tumor mass that may be facilitating invasion. Interestingly, cells along the outer edges of a tumor mass exhibit a more mesenchymal phenotype, with reduced E-cadherin, β-catenin, and cytokeratin expression and increased vimentin expression. Conversely, cells in the center of a tumor mass retain a higher expression of the epithelial markers E-cadherin and cytokeratin and little to no expression of vimentin, a mesenchymal marker. We also detected inverse expression changes in the miR-200 family and the EMT-associated transcription factors ZEB1 and SNAI1, suggesting that cSCC EMT dynamics are regulated in a miRNA-dependent manner. These novel findings in cSCC tumors provide evidence of phenotypic plasticity of the EMT process occurring within patient tissues, and extend the characterization of a hybrid EMT program occurring within a tumor mass. This hybrid EMT program may be promoting both survival and invasiveness of the tumors. A better understanding of this hybrid EMT process may influence therapeutic strategies in more invasive disease.

Collective cell migration (CCM) is a coordinated process involving cell–cell and cell–environment interactions occurring in many physiological systems, including development, wound healing, and metastasis. Using zebrafish keratocytes as a wound healing model provides a unique system to investigate the interplay of matrix metalloproteinases (MMPs) in CCM. MMPs play an important role in CCM as they generate bioactive molecules that regulate proliferation, differentiation, angiogenesis, apoptosis, and cell migration. Secreted as pro-enzymes, MMPs must be activated, frequently by another MMP. As a group, MMPs have been reported to have a pro-migratory role during CCM, yet our data reveal that one MMP, MMP13, is not pro-migratory. Treatment of keratocytes with recombinant MMP13 resulted in a dose-dependent decrease in migration, reduced MMP13 activity, and increased MMP9 mRNA expression. Treatment with an MMP13-specific inhibitor resulted in a dose-dependent increase in migration with no change in the rate of cellular proliferation, an increase in total MMP activity, and increased MMP2 mRNA expression. Similarly, inhibition of MMP14 also resulted in a significant, dose-dependent decrease in migration. However, MMP14 inhibition resulted in both an increase in MMP2 mRNA expression and a decrease in MMP9 mRNA expression. The increase in MMP2 and/or MMP9 activity was observed on gel zymography for both treatments. Our data support the hypothesis that MMP13 is anti-migratory while MMP2, MMP9 and MMP14 have a pro-migratory effect on zebrafish keratocytes. Taken together, our results outline a novel inhibitory role for MMP regulation of CCM that has implications for many other processes in multicellular organisms.