Conservative mitotic localization and functions of the nucleolar RPF2/Non3 protein in human and Drosophila cells

Svetlana V. Maltseva¹, Evgenia S. Omelina², Julia V. Popova³, Gera A. Pavlova⁴, Lybov A. Yarinich⁵, Alena V. Razuvaeva⁶, Anastasia A. Yushkova⁷, Anna A. Ogienko⁸, Alexey V. Pindyurin⁹, Evgenia N. Andreyeva^10
1Institute of Molecular and Cellular Biology SB RAS, Novosibirsk State University Novosibirsk, Russian Federation, smaltseva@mcb.nsc.ru
²Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russian Federation, omelina@mcb.nsc.ru
³Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russian Federation, popova@mcb.nsc.ru
⁴Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russian Federation, gera.pavlova@mcb.nsc.ru
⁵Institute of Molecular and Cellular Biology SB RAS, Novosibirsk State University Novosibirsk, Russian Federation, l.yarinich@mcb.nsc.ru
⁶Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russian Federation, alena.razuvaeva@mcb.nsc.ru
⁷Institute of Molecular and Cellular Biology SB RAS, Novosibirsk State University Novosibirsk, Russian Federation, a.yushkova@g.nsu.ru
⁸Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russian Federation, ogienko.anna@mcb.nsc.ru
⁹Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russian Federation, a.pindyurin@mcb.nsc.ru
¹⁰Institute of Molecular and Cellular Biology SB RAS, Novosibirsk, Russian Federation, andreeva@mcb.nsc.ru

The nucleolus is a non-membrane nuclear organelle playing a crucial role in ribosome biogenesis in eukaryotes. Its morphology and function are associated with cell growth and proliferation, as well as with cell cycle regulation. Besides that, a set of nucleolar proteins are also known to be directly involved in mitotic cell division, taking a part in the spindle assembly. Among them is the human RRS1 (Ribosome biogenesis regulator 1 homolog) protein that function in complex with RPF2 (Ribosome production factor 2 homolog) in the ribosome biogenesis pathway. Here, we report the characterization of the mitotic localization and function of the human RPF2 and its Drosophila ortholog, the Non3 (Novel nucleolar protein 3) protein. We demonstrated that depletion of RPF2 using siRNA specific to all its splicing variants leads to abnormal mitotic chromosome segregation in HeLa S3 cells. Similarly, the RNAi-mediated depletion of Non3 in Drosophila S2 cells also resulted in mitotic spindle defects including those in sister chromatid separation and segregation. Thereby, it will be possible to investigate mitotic functions of the RPF2 protein in Drosophila model system.