Genome-wide histone modification patterns in Kluyveromyces Lactis reveal evolutionary adaptation of a heterochromatin-associated mark [preprint]

The packaging of eukaryotic genomes into nucleosomes plays critical roles in all DNA-templated processes, and chromatin structure has been implicated as a key factor in the evolution of gene regulatory programs. While the functions of many histone modifications appear to be highly conserved throughout evolution, some well-studied modifications such as H3K9 and H3K27 methylation are not found in major model organisms such as Saccharomyces cerevisiae, while other modifications gain/lose regulatory functions during evolution. To study such a transition we focused on H3K9 methylation, a heterochromatin mark found in metazoans and in the fission yeast S. pombe, but which has been lost in the lineage leading to the model budding yeast S. cerevisiae. We show that this mark is present in the relatively understudied yeast Kluyveromyces lactis, a Hemiascomycete that diverged from S. cerevisiae prior to the whole-genome duplication event that played a key role in the evolution of a primarily fermentative lifestyle. We mapped genome-wide patterns of H3K9 methylation as well as several conserved modifications. We find that well-studied modifications such as H3K4me3, H3K36me3, and H3S10ph exhibit generally conserved localization patterns. Interestingly, we show H3K9 methylation in K. lactis primarily occurs over highly-transcribed regions, including both Pol2 and Pol3 transcription units. We identified the H3K9 methylase as the ortholog of Set6, whose function in S. cerevisiae is obscure. Functionally, we show that deletion of KlSet6 does not affect highly H3K9me3-marked genes, providing another example of a major disconnect between histone mark localization and function. Together, these results shed light on surprising plasticity in the function of a widespread chromatin mark

Lacerated Lips and Lush Landscapes: Constructing This-Worldly Theological Identities in the Otherworld

When Irenaeus juxtaposed tradition and heresy, he moved away from the Pauline usage, which centered primarily upon incorrect behavior (See 1 Cor 11: 19, Gal 5 :20). lrenaeus\u27 definition of heresy, however, does not indicate that all early Christians prioritized belief over behavior, or even maintained orthodoxy and orthopraxis as separate categories. In the otherworldly spaces of the apocryphal apocalypses doxa and praxis seem to be intertwined, and little or no distinction is made between belief and behavior. Instead, in the Otherworld the categories of primary importance are righteous/unrighteous, good/evil, Christian/Other. The Otherworld is a place in which sins can be sorted and the identity markers which might have been overlooked or are difficult to see in this world can be seen more clearly. And yet, we are left to wonder how that otherworldly clarity maps onto the lived experience of the ancient audiences of these apocalypses. Thus, we will begin by reflecting upon the ability of these apocalyptic texts to create (and recreate) Christian identity by either describing real categories of people, or by creating the categories themselves, and so prescribing reality. In each of the apocalypses that we will discuss the reader learns that his or her identity is determined for all of eternity by the choices that are made in this world. In this regard, each depiction of the otherworld establishes its own identity markers, isolating certain beliefs and behaviors as distinctively Christian. What is startling about the definitions of Christian belief and practice that emerge from each text is that they are rather expansive, covering far more territory than any creed or council. Our discussion will demonstrate that while creedal definitions of orthodoxy ( as well as the apocalyptic definitions of correct belief that mirror them) were often aimed at labeling specific groups as other, the apocalyptic depictions of the otherworld were attempting to be either exhaustive or open-ended, imagining a host of practices that could be used to frame Christian identity. In these imaginary spaces, the theological identities that were crafted could not simply be summarized by simple binaries like orthodoxy/heterodoxy, oppressed/oppressor, or even sinner/sinless. Instead, the apocalyptic visions, which on the surface seem to deal in dichotomies, paradoxically proliferate a range of Christian practices