Ensemble Methods for Identifying RNA Operons and Regulons in the Clock Network of Neurospora Crassa

Abstract

With both light entrainment data (L/D) and free running data in the dark (D/D), Variable Topology Ensemble Methods (VTENS) were used to reconstruct the entire genome-scale clock network involving 3380 genes and their products under the hypothesis that clock-controlled genes are both transcriptionally regulated and post-transcriptionally regulated through RNA operons. The clock network has 12 hubs with target genes surrounding twelve regulators, and 694 putative clock-controlled genes provide linkage between hubs in their joint regulation. There were 71 significant feedforward loops within this clock network, the majority of which involved genes lhp-1 and NCU06108 targeting genes connected with the ribosome and ribosome biogenesis. All 12 regulators target amino acid biosynthesis. The largest hub (768 genes) surrounded the post-transcriptional regulator lhp-1 defining an RNA operon. There appears to be no partitioning of light-regulated genes and circadian genes between the 12 hubs. The regulators lhp-1, has-1, and rrp-3 appear to target putative clock-controlled genes in ribosome biogenesis. The combined hypothesis of 6 RNA operons and 5 transcriptional regulons was successful in describing the dynamics of the clock network with 3380 genes and their products with a $\chi ^{2} =2.133$ per data point for 60,759 mRNA time points. With little known about allosteric regulation of metabolism, the clock network provided a major link between gene regulation and metabolism.

Keywords

• Variable topology ensemble methods
• supernet
• RNA operon
• has-1
• lhp-1
• ribosome biogenesis