Novel Cell-Penetrating Peptides Derived From Scaffold-Attachment- Factor A Inhibits Cancer Cell Proliferation and Survival

Abstract

Scaffold-attachment-factor A (SAFA) has important roles in many normal and pathologic cellular processes but the scope of its function in cancer cells is unknown. Here, we report dominant-negative activity of novel peptides derived from the SAP and RGG-domains of SAFA and their effects on proliferation, survival and the epigenetic landscape in a range of cancer cell types. The RGG-derived peptide dysregulates SAFA binding and regulation of alternatively spliced targets and decreases levels of key spliceosome proteins in a cell-type specific manner. In contrast, the SAP-derived peptide reduces active histone marks, promotes chromatin compaction, and activates the DNA damage response and cell death in a subset of cancer cell types. Our findings reveal an unprecedented function of SAFA-derived peptides in regulating diverse SAFA molecular functions as a tumor suppressive mechanism and demonstrate the potential therapeutic utility of SAFA-peptides in a wide range of cancer cells.

hnRNPK-derived cell-penetrating peptide inhibits cancer cell survival

“…Our published work shows that a dominant-negative peptide derived from the RGG domain of SAFA (hnRNPU) has effects on cancer cell survival, histone marks, and other key processes that are similar to those of CPP-hnRNPK-RGG. 42 , 43 Despite the similarity in structure between the RGG domain of hnRNPK and hnRNPU and those of other hnRNPs, peptides derived from the RGG domains of hnRNPA1 and hnRNPF had no effect on survival of the cancer cells we tested. It could be that these hnRNPs have more limited roles in cancer cells and/or that their RGG domains have molecular functions different from those of hnRNPK and hnRNPU.…”

“…Previously, we showed that treatment of these cancer lines with hnRNPU-RGG-derived peptide resulted in decreased expression of E2F1-responsive genes and perturbed the cell cycle in a cell-type-specific manner. 42 Others have shown that hnRNPK loss of function leads to reduced expression of cell-cycle genes, blocking the cell cycle at different stages depending on cell type. 53 , 54 In the case of CPP-hnRNPK-RGG-treated cells, flow cytometry analysis of propidium iodide-stained cells showed no alteration in cell-cycle distribution relative to CPP-Neg, with the exception of a slight increase in HT1080 cells in S phase ( Figure S3A ).…”

“…However, many of these interventions are directed at molecules and processes that are also required in normal cells, resulting in significant toxicity. We have shown that dominant-negative peptides derived from the RNA-binding domains of hnRNPU and RBM39 (also known as CAPERα) have minimal effects on normal cells because they disrupt cancer-cell-specific interactions and molecular functions 42 , 43 and may have significant clinical advantages over less targeted approaches. Here, we provide support for further exploration and development of a peptide with dominant-negative functions in hnRNPK, called CPP-hnRNPK-RGG, as a therapeutic peptide.…”

“…Crystal violet staining was performed as in Puvvula and Moon. 42 Briefly, cells were grown in six-well plates in complete growth medium. When they reached 60% confluence, the growth medium was replaced with Opti-MEM medium supplemented with peptide at the concentrations shown in the figure legends.…”

“… 41 We recently developed novel RBM39- and hnRNPU-derived dominant-negative CPPs that reduce the survival and proliferation of a range of cancer cells. 42 , 43 We have demonstrated that RBM39-derived CPPs disrupt its interaction with the MLL1 complex and its DNA targets, while a peptide derived from the RGG domain of SAFA (also known as hnRNPU) disrupts its interaction with target RNAs. In both cases, the resulting effects on the epigenetic landscape, transcription, and splicing decrease the growth and survival of multiple types of cancer cells while leaving normal cells unharmed.…”