Uncovering Hidden Layers of Cell Cycle Regulation through Integrative Multi-omic Analysis

Studying the complex relationship between transcription, translation and protein degradation is essential to our understanding of biological processes in health and disease. The limited correlations observed between mRNA and protein abundance suggest pervasive regulation of post-transcriptional steps and support the importance of profiling mRNA levels in parallel to protein synthesis and degradation rates. In this work, we applied an integrative multi-omic approach to study gene expression along the mammalian cell cycle through side-by-side analysis of mRNA, translation and protein levels. Our analysis sheds new light on the significant contribution of both protein synthesis and degradation to the variance in protein expression. Furthermore, we find that translation regulation plays an important role at S-phase, while progression through mitosis is predominantly controlled by changes in either mRNA levels or protein stability. Specific molecular functions are found to be co-regulated and share similar patterns of mRNA, translation and protein expression along the cell cycle. Notably, these include genes and entire pathways not previously implicated in cell cycle progression, demonstrating the potential of this approach to identify novel regulatory mechanisms beyond those revealed by traditional expression profiling. Through this three-level analysis, we characterize different mechanisms of gene expression, discover new cycling gene products and highlight the importance and utility of combining datasets generated using different techniques that monitor distinct steps of gene expression.
Author Summary How the genetic program of a cell unfolds to execute complex functions depends on a dynamic interplay between multiple steps that include transcription of DNA into mRNA, translation of mRNA into protein and post-translational degradation of mature proteins. Profiling of gene expression is traditionally based on measurements of steady-state mRNA levels, but recent studies have shown that mRNA and protein levels are highly discordant, suggesting that post-transcriptional mechanisms play a dominant role in modulating protein abundance. Here we combine measurements of mRNA, translation and protein across the mammalian cell cycle to uncover the hidden complexity of cell cycle regulation. Using this approach, we gain insights into the dynamics of protein synthesis and degradation and identify new genes and functions that cycle through cell division by periodic changes in translation or degradation rates. Integrative multi-omic analyses combining information on the transcriptome, translatome and proteome hold great promise for providing transformative biological insights in a variety of model systems.