GSE174115
Targeting MYC Transcription with Small Peptide Derived from KSHV Transactivator (SLAM-Seq)
Herpesviruses rely on host cell transcription and translation machineries for replication. Viral proteins thus function to redirect multiple cellular proteins for viral replication. In herpesvirus replicating cells, host cell gene transcription is frequently down-regulated because important transcriptional apparatuses are appropriated by viral transcription factors. Here we show that an evolutionally-shaped viral protein sequence is a great starting material for unique drug development to modulate cellular transcription. Cellular c-Myc protein (MYC) is overexpressed in over 70% of all types of cancer cells and therefore a very attractive target to control cancer cell growth. We identified a small functional peptide derived from the Kaposi's sarcoma-associated herpesvirus transactivator (K-Rta), which strongly attenuates MYC expression, reduces cell proliferation, and selectively kills cancer cells in both tissue culture and a xenograft tumor mouse model. Mechanistically, the peptide blocks promoter-enhancer interactions by preventing coactivator complex consisting of Nuclear receptor coactivator 2, p300, and SWI/SNF proteins from engaging the MYC promoter in leukemia cells. Target gene profiling with SLAM-seq suggests that the viral peptide attenuates MYC expression through a mechanism likely different from that of BET bromodomain inhibitors. Furthermore, fusing the 13 amino acids peptide with humanized anti-CD22 single chain armed the antibody drug with cell killing ability, and inhibited cell growth in soft agar. Our studies thus demonstrate the utility of the peptide sequence as a therapeutics module, which may be used to modulate MYC activity in a cell type-specific manner. Overall design: The goal of these studies was to utilize thiol(SH )-linked alkylation for the metabolic sequencing of RNA (SLAM-seq) in order to determine the dynamics of gene expression in response to treatment with a novel small functional peptide therapeutic derived from the Kaposi's sarcoma-associated herpesvirus (KSHV)-transactivator (K-Rta), which strongly attenuates MYC expression. This was performed in the context of the BCBL-1 and BC-1 cell line models, which are derived from KSHV-infected human primary effusion lymphomas (PEL) and contain latent KSHV genomes. For this study, replicate cultures from each cell line were treated with either vehicle control, wild-type peptide (24 uM), or mutant peptide (24 uM) for 30 minutes, and then for an additional 1 hour in the presence of 4-Thiouridine (s4U; 300 uM) in order to label nascent transcripts. Following treatment, the cells were then harvested for isolation of total RNA (containing s4Uracil-labeled transcripts) and followed by library preparation and next-generation sequencing (NGS).