Integrative data analysis indicates an intrinsic disordered domain character of Argonaute-binding motifs

SPT6L, a newly discovered ancestral component of the plant RNA-directed DNA methylation pathway

RNA-directed DNA methylation (RdDM) is driven by small RNAs (sRNAs) complementary to the nascent transcript of RNA polymerase V (Pol V). sRNAs associated with ARGONAUTE (AGO) proteins are tethered to Pol V mainly by the AGO-hook domain of its subunit NRPE1. We found, by in silico analyses, that Pol V strongly colocalizes on chromatin with another AGO-hook protein, SPT6-like (SPT6L), which is a known essential transcription elongation factor of Pol II. Our phylogenetic analysis revealed that SPT6L acquired its AGO-binding capacity already in the most basal streptophyte algae, even before the emergence of Pol V, suggesting that SPT6L might be a driving force behind the RdDM evolution. Since its emergence, SPT6L with the AGO-hook represents the only conserved SPT6 homolog in Viridiplantae, implying that the same protein is involved in both Pol II and Pol V complexes. To better understand the role of SPT6L in the Pol V complex, we characterized genomic loci where these two colocalize and uncovered that DNA methylation there is more dynamic, driven by higher levels of sRNAs often from non-canonical RdDM pathways and more dependent on chromatin modifying and remodeling proteins like MORC. Pol V loci with SPT6L are highly depleted in helitrons but enriched in gene promoters for which locally and temporally precise methylation is necessary. In view of these results, we discuss potential roles of multiple AGO-hook domains present in the Pol V complex and speculate that SPT6L mediates de novo methylation of naïve loci by interconnecting Pol II and Pol V activities.

Stimulating Intrinsic Motivation in Millennial Students: A New Generation, a New Approach

There has been a fundamental change in health care pedagogy to address the demands and challenges posed by the present generation of millennial students. There is also a growing recognition of the role of intrinsic motivation as a catalyst in a positive learning experience. The term intrinsic motivation refers to energizing behavior that comes from within an individual and develops due to an inherent interest in the activity at hand. However, stimulating intrinsic motivation in the present generation of millennial health care students is a daunting task, considering their diverse and disparate nature. In addition, the inherent generational differences between educators and students, and an increasing emphasis on technological tools have resulted in a dichotomy in the educational environment leading to the development of a greater incidence of burnouts among students. Hence, numerous innovative techniques have been introduced in health care education to enhance the levels of intrinsic motivation in these students. Unfortunately, most of these approaches have only been moderately successful due to their limited ability to address the unique educational expectations of millennial students. The cumulative evidence suggests that specific approaches to stimulate intrinsic motivation should aim at nurturing the learning efforts of students, bridging the generational barriers between educators and students, and ameliorating the stress associated with health care education. Hence, the specific aim of this narrative review is to suggest empirically proven curricular strategies and institutional reforms to enhance intrinsic motivation in health care students belonging to the Millennial Generation.

Identification and Analysis of WG/GW ARGONAUTE-Binding Domains

WG/GW domains recruit ARGONAUTE (AGO) proteins to distinct silencing effector complexes using combinations of just two amino acids: tryptophan (W) and glycine (G), forming a wide arsenal of highly simplified interaction surfaces. These unstructured domains exhibit very low sequence identity and excessive length polymorphism, which makes identification of new AGO-binding proteins a challenging task as they escape detection with standard sequence comparison-based methods (e.g., BLAST, HMMER).In this chapter, we explain the use of tools for prediction of AGO-binding WG/GW domains in protein sequences. We also show how to computationally explore an up-to-date information about AGO-interacting proteins and discover new properties of WG/GW domains. Finally, we encourage readers to explore the game-like web application for in silico designing/modifying AGO-binding sequences as well as modeling mutagenesis experiments and predicting their potential effect on AGO-binding activity.

Early origin and adaptive evolution of the GW182 protein family, the key component of RNA silencing in animals

The GW182 proteins are a key component of the miRNA-dependent post-transcriptional silencing pathway in animals. They function as scaffold proteins to mediate the interaction of Argonaute (AGO)-containing complexes with cytoplasmic poly(A)-binding proteins (PABP) and PAN2-PAN3 and CCR4-NOT deadenylases. The AGO-GW182 complexes mediate silencing of the target mRNA through induction of translational repression and/or mRNA degradation. Although the GW182 proteins are a subject of extensive experimental research in the recent years, very little is known about their origin and evolution. Here, based on complex functional annotation and phylogenetic analyses, we reveal 448 members of the GW182 protein family from the earliest animals to humans. Our results indicate that a single-copy GW182/TNRC6C progenitor gene arose with the emergence of multicellularity and it multiplied in the last common ancestor of vertebrates in 2 rounds of whole genome duplication (WGD) resulting in 3 genes. Before the divergence of vertebrates, both the AGO- and CCR4-NOT-binding regions of GW182s showed significant acceleration in the accumulation of amino acid changes, suggesting functional adaptation toward higher specificity to the molecules of the silencing complex. We conclude that the silencing ability of the GW182 proteins improves with higher position in the taxonomic classification and increasing complexity of the organism. The first reconstruction of the molecular journey of GW182 proteins from the ancestral metazoan protein to the current mammalian configuration provides new insight into development of the miRNA-dependent post-transcriptional silencing pathway in animals.