Drosophila LTV1 (Low Temperature Viability Protein 1) is Required for Ribosome Biogenesis and Cell Growth Downstream of dMyc [Cell Biology]

April 9th, 2015 by Kim, W., Kim, H. D., Jung, Y., Kim, J., Chung, J.

During animal development, various signaling pathways converge to regulate cell growth. In this study, we identify LTV1 as a novel cell growth regulator in Drosophila. LTV1 mutant larvae exhibit developmental delays and lethality at the second larval stage. Using biochemical studies, we discover that LTV1 interacts with ribosomal protein S3 (RpS3) and co-purifies with free 40S ribosome subunits. We further demonstrate that LTV1 is crucial for ribosome biogenesis through 40S ribosome subunit synthesis and pre-ribosomal RNA processing, suggesting that LTV1 is required for cell growth by regulating protein synthesis. We also demonstrate that Drosophila Myc (dMyc) directly regulates LTV1 transcription and requires LTV1 to stimulate ribosome biogenesis. Importantly, the loss of LTV1 blocks the cell growth and endoreplication induced by dMyc. Combined, these results suggest that LTV1 is a key downstream factor of dMyc-induced cell growth by properly maintaining ribosome biogenesis.