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Autophagy is an evolutionarily conserved degradation mechanism of misfolded proteins and damaged organelles which helps maintain cellular homeostasis. Besides its canonical function, proteins of the autophagy pathway also participate in other cellular processes including chromosome congression. Here, we perform a comprehensive screen of autophagy mutants in yeast and found that cells lacking an autophagy-related protein Atg11 have poor mitotic stability of linear and circular chromosomes. atg11Δ cells grow slowly at 37°C and accumulate at metaphase with aberrant astral microtubules (aMTs) along with mispositioned and misaligned spindles. Deletion of the spindle positioning checkpoint (SPOC) factor Bub2, but not the spindle assembly checkpoint (SAC) component Mad2, could improve the growth of the atg11Δ cells. Strikingly, the spindle pole body (SPB) localization pattern of an SPB component Spc72 is found to be randomized in atg11Δ cells resulting in inverted SPB inheritance. Atg11 is transiently localized to SPBs and interacts both physically and genetically with Spc72. Taken together, our study uncovers a moonlighting function of Atg11 participating between spatially separated processes, the cell cycle and autophagy, essential for proper spindle positioning and asymmetric SPB inheritance. Our findings, therefore, highlight one of the many failsafe mechanisms likely in place to ensure asymmetric cell division.

Spermatogenesis is characterized by sequential gene-expression at precise stages in progression of differentiation of the germ cells. Any alteration in expression of the critical genes is responsible for arrest of spermatogenesis associated with infertility. Inspite of advances the differential gene expression accompanying spermatogenesis, the corresponding regulatory mechanisms and their correlation to human infertility have not been clearly established. This study aims to identify the gene expression pattern of the human testicular germ cells from the patients either with obstructive azoospermia with complete intra-testicular spermatogenesis or non-obstructive azoospermia with spermatogenesis arrested at different stages and correlate the same to infertility. The testicular transcriptomes of 3 OA and 8 NOA patients and pooled testicular RNA (commercial source) were analyzed for their differential gene expression to identify potential regulators of spermatogenesis and the results were further validated in all of the 44 patients clinically diagnosed with azoospermia undergoing sperm retrieval surgery over the study period and 4 control samples included in this study. Analyses of the differential transcriptome led to identification of genes enriched in a specific testicular cell type and subsequently, several regulators of the diploid-double-diploid-haploid transitions in the human spermatogenesis were identified. Perturbations in the expression of these genes were identified as the potential causes of the spermatogenic arrest seen in azoospermia and thus the potential mediators of human male infertility. Another interesting observation was the increased autophagy in the testes of patients with non-obstructive azoospermia. The present study suggests that the regulation of the diploid-double-diploid-haploid transition is multigenic with the tandem alteration of several genes resulting in infertility. In conclusion, this study identified some of the genetic regulators controlling spermatogenesis using comparative transcriptome analyses of testicular tissues from azoospremic individuals and showed how alterations in several genes results in disruption of spermatogenesis and subsequent infertility. This study also provides interesting insights into the gene expression patterns of the Indian population that were not available earlier.

During autophagy, double membrane vesicles called autophagosomes capture and degrade the intracellular cargo. The de novo formation of autophagosomes requires several vesicle transport and membrane fusion events which are not completely understood. We studied the involvement of Exocyst- an octameric tethering complex, which has a primary function in tethering post-Golgi secretory vesicles to plasma membrane, in autophagy. Our findings indicate not all subunits of exocyst are involved in selective and general autophagy. We show that in the absence of autophagy specific subunits, autophagy arrest is accompanied by accumulation of incomplete autophagosome-like structures. In these mutants, impaired Atg9 trafficking leads to decreased delivery of membrane to the site of autophagosome biogenesis thereby impeding the elongation and completion of the autophagosomes. The subunits of exocyst which are dispensable for autophagic function do not associate with the autophagy specific subcomplex of exocyst.

Multifunctional human transcriptional positive co-activator 4 (PC4) is a bonafide non-histone component of the chromatin and plays a pivotal role in the process of chromatin compaction and functional genome organization. Knockdown of PC4 expression leads to a drastic open conformation of the chromatin and thereby altered nuclear architecture, defects in chromosome segregation and changed epigenetic landscape. Interestingly, these defects do not induce cellular death but result in enhanced cellular proliferation possibly through enhanced autophagic activity. PC4 depletion confers significant resistance to gamma irradiation. Exposure to gamma irradiation further induced autophagy in these cells. Inhibition of autophagy by small molecule inhibitors as well as by silencing of a critical autophagy gene drastically reduces the survivability PC4 knockdown cells. On the contrary, complementation with wild type PC4 could reverse this phenomenon, confirming the process of autophagy as the key mechanism for radiation resistance in absence of PC4. These data connect the unexplored role of chromatin architecture in regulating autophagy during a stress condition such as radiation.

Autophagy is a conserved cellular degradation pathway wherein a double membrane vesicle, called as an autophagosome captures longlived proteins, damaged or superfluous organelles and delivers to the lysosome for degradation1. We have identified a novel role for septins in autophagy. Septins are GTP-binding proteins that localize at the bud-neck and are involved in cytokinesis in budding yeast2. We show that septins under autophagy prevalent conditions are majorly localized to the cytoplasm in the form of punctate structures. Further, we report that septins not only localize to pre-autophagosomal structure (PAS) but also to autophagosomes in the form of punctate structures. Interestingly, septins also form small non-canonical rings around PAS during autophagy. Furthermore, we observed that in one of the septin Ts" mutant,cdc10-5, the anterograde trafficking of Atg9 was affected at the non-permissive temperature (NPT). All these results suggest a role of septins in early stages of autophagy during autophagosome formation.