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Extracellular vesicles (EVs) laden with lipids, proteins, DNA, and micro-RNAs play important biological functions in intercellular communication and have pivotal roles in pathophysiological conditions. Characterization of the EVs has always been a multistep process involving large volumes, and they are heterogeneous in size and properties. A multitude of approaches is used to distinguish the EVs. Here, we report simple citrate reduced silver nanoparticles assisted surface-enhanced Raman spectroscopy (SERS) as a tool to distinguish EVs extracted from several cell lines isolated under autophagic conditions (nitrogen starvation). This study is the first report of its kind in characterizing EVs from cells under autophagic conditions using SERS. We used two cancerous cell lines, HeLa, its corresponding autophagy-deficient cell line (Atg5-/-), and a noncancerous cell line, HEK293, to isolate EVs. Our study helps in the facile detection and differentiation of EVs isolated between two closely related human cell lines that differ by their autophagic ability. The principal component analysis (PCA) of the SERS spectra of these EVs consistently showed the presence of distinct chemical compositions of the EVs. SERS of EVs can help in probing more into the molecular level information from EVs and could become a powerful tool once coupled with improved microscopy techniques for diagnosis and therapy.

DNA replication in eukaryotes is initiated by the orchestrated assembly and association of initiator proteins (heterohexameric Origin Recognition Complex, ORC) on the replication origins. These functionally conserved proteins play significant roles in diverse cellular processes besides their central role in ignition of DNA replication at origins. WhileCandida albicans, a major human fungal pathogen, is an ascomycetous, asexual, diploid budding yeast but it is significantly diverged from a much better studied model organismSaccharomyces cerevisiae. The components of the DNA replication machinery inC. albicansremain largely uncharacterized. Identification of factors required for DNA replication is essential for understanding the evolution of the DNA replication machinery. We identified the putative ORC homologs inC. albicansand determined their relatedness with those of other eukaryotes including several yeast species. Our extensivein silicostudies demonstrate that the domain architecture of CaORC proteins share similarities with the ORC proteins ofS. cerevisiae. We dissect the domain organization of ORC (trans-acting factors) proteins that seem to associate with DNA replication origins inC. albicans. We present a model of the 3D structure of CaORC4 to gain further insights of this protein’s function.

Autophagy is an evolutionarily conserved intracellular degradation process in which cytoplasmic components are captured in double membrane vesicles called autophagosomes and delivered to lysosomes for degradation. This process has an indispensable role in maintaining cellular homeostasis. The rate at which the dynamic turnover of cellular components takes place via the process of autophagy is called autophagic flux. In this review, we discuss about the orchestrated events in the autophagy process, transcriptional regulation, role of autophagy in some major human diseases like cancer, neurodegeneration (aggrephagy), and pathogenesis (xenophagy). In addition, autophagy has non-canonical roles in protein secretion, thus demonstrating the multifaceted role of autophagy in intracellular processes.

Unconventional protein secretion (UPS) is an important phenomenon with fundamental implications to cargo export. How eukaryotic proteins transported by UPS are recognized without a conventional signal peptide has been an open question. It was recently observed that a diacidic amino acid motif (ASP-GLU or DE) is necessary for the secretion of superoxide dismutase 1 (SOD1) from yeast under nutrient starvation. Taking cue from this discovery, we explore the hypothesis of whether the diacidic motif DE, which can occur fairly ubiquitously, along with its context, can be a generic signal for unconventional secretion of proteins. Four different contexts were evaluated: a physical context encompassing the structural order and charge signature in the neighbourhood of DE, two signalling contexts reflecting the presence of either a phosphorylatable amino acid (‘X’ in XDE, DXE, DEX) or an LC3 interacting region (LIR) which can trigger autophagy and a co-evolutionary constraint relative to other amino acids in the protein interpreted by examining sequences across different species. Among the 100 proteins we curated from different physiological or pathological conditions, we observe a pattern in the unconventional secretion of heat shock proteins in the cancer secretome, where DE in an ordered structural region has higher odds of being a UPS signal.

The centromere, on which kinetochore proteins assemble, ensures precise chromosome segregation. Centromeres are largely specified by the histone H3 variant CENP-A (also known as Cse4 in yeasts). Structurally, centromere DNA sequences are highly diverse in nature. However, the evolutionary consequence of these structural diversities on de novo CENP-A chromatin formation remains elusive. Here, we report the identification of centromeres, as the binding sites of four evolutionarily conserved kinetochore proteins, in the human pathogenic budding yeast Candida tropicalis. Each of the seven centromeres comprises a 2 to 5 kb non-repetitive mid core flanked by 2 to 5 kb inverted repeats. The repeat-associated centromeres of C. tropicalis all share a high degree of sequence conservation with each other and are strikingly diverged from the unique and mostly non-repetitive centromeres of related Candida species—Candida albicans, Candida dubliniensis, and Candida lusitaniae. Using a plasmid-based assay, we further demonstrate that pericentric inverted repeats and the underlying DNA sequence provide a structural determinant in CENP-A recruitment in C. tropicalis, as opposed to epigenetically regulated CENP-A loading at centromeres in C. albicans. Thus, the centromere structure and its influence on de novo CENP-A recruitment has been significantly rewired in closely related Candida species. Strikingly, the centromere structural properties along with role of pericentric repeats in de novo CENP-A loading in C. tropicalis are more reminiscent to those of the distantly related fission yeast Schizosaccharomyces pombe. Taken together, we demonstrate, for the first time, fission yeast-like repeat-associated centromeres in an ascomycetous budding yeast., Author Summary Centromeres aid in high fidelity chromosome segregation. Paradoxically, centromere DNA sequences are rapidly evolving in fungi, plants, and animals. Centromere DNA sequences in fungi can be unique in each chromosome or share conserved features such as motifs for sequence specific protein binding, pericentric repeats, or transposon-rich elements. Ascomycetous fungi, in particular, show a wide range of diversity in centromere sequence elements. However, no ascomycetous budding yeast species is known to possess repeat-associated centromeres in all of its chromosomes. Here, we identified and mapped all seven centromeres in an ascomycete, a rapidly emerging human pathogenic yeast, Candida tropicalis. The repeat-associated centromeres of highly homogeneous DNA sequences in C. tropicalis are significantly diverged from the mostly non-repetitive unique centromeric DNA sequences of its closely related sequenced species, Candida albicans, Candida dubliniensis and Candida lusitaniae. Structurally, the centromeres of C. tropicalis more closely resemble those of the distantly related fission yeast Schizosaccharomyces pombe. Thus, we discover rapidly diverging repeat-associated centromeres in an ascomycetous budding yeast and provide evidence of emergence of repeat-associated centromeres via two independent evolutionary events in ascomycetous fungi.

The Cse4p-containing centromere regions of Candida albicans have unique and different DNA sequences on each of the eight chromosomes. In a closely related yeast, C. dubliniensis , we have identified the centromeric histone, CdCse4p, and shown that it is localized at the kinetochore. We have identified putative centromeric regions, orthologous to the C. albicans centromeres, in each of the eight C. dubliniensis chromosomes by bioinformatic analysis. Chromatin immunoprecipitation followed by PCR using a specific set of primers confirmed that these regions bind CdCse4p in vivo . As in C. albicans , the CdCse4p-associated core centromeric regions are 3–5 kb in length and show no sequence similarity to one another. Comparative sequence analysis suggests that the Cse4p-rich centromere DNA sequences in these two species have diverged faster than other orthologous intergenic regions and even faster than our best estimated “neutral” mutation rate. However, the location of the centromere and the relative position of Cse4p-rich centromeric chromatin in the orthologous regions with respect to adjacent ORFs are conserved in both species, suggesting that centromere identity is not solely determined by DNA sequence. Unlike known point and regional centromeres of other organisms, centromeres in C. albicans and C. dubliniensis have no common centromere-specific sequence motifs or repeats except some of the chromosome-specific pericentric repeats that are found to be similar in these two species. We propose that centromeres of these two Candida species are of an intermediate type between point and regional centromeres.

Background Replication and transcription, the two key functions of DNA, require unwinding of the DNA double helix. It has been shown that replication origins in the budding yeast, Saccharomyces cerevisiae contain an easily unwound stretch of DNA. We have used a recently developed method for determining the locations and degrees of stress-induced duplex destabilization (SIDD) for all the reported replication origins in the genome of the fission yeast, Schizosaccharomyces pombe. Results We have found that the origins are more susceptible to SIDD as compared to the non-origin intergenic regions (NOIRs) and genes. SIDD analysis of many known origins in other eukaryotes suggests that SIDD is a common property of replication origins. Interestingly, the previously shown deletion-dependent changes in the activities of the origins of the ura4 origin region on chromosome 3 are paralleled by changes in SIDD properties, suggesting SIDD’s role in origin activity. SIDD profiling following in silico deletions of some origins suggests that many of the closely spaced S. pombe origins could be clusters of two or three weak origins, similar to the ura4 origin region. Conclusion SIDD appears to be a highly conserved, functionally important property of replication origins in S. pombe and other organisms. The distinctly low SIDD scores of origins and the long range effects of genetic alterations on SIDD properties provide a unique predictive potential to the SIDD analysis. This could be used in exploring different aspects of structural and functional organization of origins including interactions between closely spaced origins.