Metazoans-like mitotic events in a human pathogenic budding yeast, cryptococcus neoformans

Abstract

The mitotic cell cycle is defined as the sequence of events that ensure equal segregation of the genetic material into two daughter cells. The mitotic cell cycle is broadly divided into two different phases, interphase and mitosis. During interphase, a cell prepares itself for division by increasing its size and necessary components required for division. Interphase is the longer phase in the cell cycle. It is further divided into 3 stages: G1 (Gap 1), S (Synthesis) and G2 (Gap 2) phase. S phase is the stage in which the DNA content of a cell is doubled by replication. Mitotic phase is the stage when segregation of DNA occurs and it is subdivided into prophase, metaphase, anaphase and telophase (Figure 1). Once the chromosome segregation is complete, cytokinesis takes place which divides a single cell into two separate daughter cells. This event marks the end of the cell cycle. Though the outcome of the mitotic cell cycle is the same in yeasts and humans, many subtle differences exist (Wang, Oliferenko et al. 2003). The stages of the cell cycle have clear boundaries in metazoans but not in yeasts. Unlike metazoans, G2 and mitotic phases are overlapping and usually defined as the G2/M stage in yeasts. The other differences between yeasts and metazoans include the extent of chromosome condensation, formation of the metaphase plate and breakdown of the nuclear envelope (NE). During mitosis, all these processes help in proper segregation of the chromosomes. Any defect in proper chromosome segregation leads to various types of complications leading to onset of diseases related to aneuploidy. Thus the role of the chromosome segregation machinery is crucial for proper execution of the cell cycle and survival of an organism. The major machineries involved in this process include the centromere/kinetochore (KT), kinetochore-microtubule (KT-MT) interaction and spindle assembly checkpoint (SAC).