From Polarity to Morphogenesis PAK Behaviors and Mechanism for Bud Sensing in Morphogenesis Checkpoint

Bud formation by Saccharomyces cerevisiae is a fundamental process for yeast proliferation. Bud emergence is initiated by the polarization of the cytoskeleton, leading to local secretory vesicle delivery and gulcan synthase activity. The master regulator of polarity establishment is a small Rho-family GTPase – Cdc42. Cdc42 forms a clustered patch at the incipient budding site in late G1 and mediates downstream events which lead to bud emergence. Cdc42 promotes morphogenesis via its various effectors. PAKs (p21-activated kinases) are important Cdc42 effectors which mediate actin cytoskeleton polarization and septin filament assembly. The PAKs Cla4 and Ste20 share common binding domains for GTP-Cdc42 and they are partially redundant in function. However, we found that Cla4 and Ste20 behaved differently during the polarization and this depended on their different membrane interaction domains. Also, Cla4 and Ste20 compete for a limited number of binding sites at the polarity patch during bud emergence. These results suggest that PAKs may be differentially regulated during polarity establishment.

Morphogenesis of yeast must be coordinated with the nuclear cycle to enable successful proliferation. Many environmental stresses temporarily disrupt bud formation, and in such circumstances, the morphogenesis checkpoint halts nuclear division until bud formation can resume. Bud emergence is essential for degradation of the mitotic inhibitor, Swe1. Swe1 is localized to the septin cytoskeleton at the bud neck by the Swe1-binding protein Hsl7. Neck localization of Swe1 is required for Swe1 degradation. Although septins form a ring at the presumptive bud site prior to bud emergence, Hsl7 is not recruited to the septins until after bud emergence, suggesting that septins and/or Hsl7 respond to a “bud sensor”. Here we show that recruitment of Hsl7 to the septin ring depends on a combination of two septin-binding kinases: Hsl1 and Elm1. We elucidate which domains of these kinases are needed, and show that artificial targeting of those domains suffices to recruit Hsl7 to septin rings even in unbudded cells. Moreover, recruitment of Elm1 is responsive to bud emergence. Our findings suggest that Elm1 plays a key role in sensing bud emergence.

“Newter”-ing the Nicodemite: Reception of John Calvin’s Quatre sermons (1552) in Sixteenth-Century England

This dissertation examines the publication history of a single work: John Calvin’s 1552 Quatre sermons de M. Jehan Calvin traictans des matières fort utiles pour nostre temps, avec briefve exposition du Pseaume lxxxvii. Overlooked for both its contribution to Calvin’s wider corpus and its surprising popularity in English translation, successive editions of Quatre sermons display how Calvin’s argument against the behavior of so-called “Nicodemites” was adapted to various purposes unrelated to refuting religious dissimulation. The present study contributes to research in Calvin’s anti-Nicodemism by highlighting the fruitfulness of focusing on a discrete work and its reception. Borrowing a term (“Newter”) from John Field’s 1579 translation of Quatre sermons, this study’s title adumbrates its argument. English translators capitalized on the intrinsic malleability of a nameless and faceless opponent, the Nicodemite, and the adaptability of Quatre sermons’ genre as a collection of sermons to reshape—or, if you will, disfigure—both Calvin’s original foes and his case against them to advance various new agenda. Yet they were not the first to use the reformer’s sermons this way. They could have learned this from Calvin himself.

My examination of Quatre sermons opens by setting the work in the context of Calvin’s other writings and his political situation (Introduction, chapters one and two). Calvin’s unrelenting literary assault on French Nicodemism over three decades has long been recognized for its consistency and negativity. Yet scholars have tended to neglect how Calvin’s polemic against religious dissimulation could exhibit significant flexibility according to the needs of his context. Whereas Calvin’s preface promises simply to revisit his previous argument against participation in the Mass, his approach to Nicodemism in Quatre sermons seems adapted to accomplish goals beyond decrying false worship, offering a carefully-crafted apology for Calvin’s pastoral authority directed at his political situation. Repeatedly emphasizing God’s purpose to bless his children through the ministry of a rightly-ordered church, Quatre sermons marks a shift in Calvin’s anti-Nicodemite rhetoric away from purely negative critique, stressing instead God’s provision of spiritual nurture via political exile. Read in light of Calvin’s 1552 context, two audiences emerge: sermons ostensibly targeting believers in France who hid their faith also appear especially designed to silence Calvin’s foes in Geneva.

The remainder of the study examines the reception of Quatre sermons in the rapidly shifting religious and social contexts of Marian and Elizabethan England, where it appeared in more unique editions than any of Calvin’s writings besides the Institutio and the reformer’s 1542/45 Genevan Catechism. Calvin’s anti-Nicodemism has not been examined for its distinct contribution to the overall English reception of his thought. Five English versions of Quatre sermons appeared between 1553 and 1584—four of these under a Protestant queen, a situation quite different from the French context Calvin addressed. After situating Calvin’s position within the currents of Tudor Protestant anti-Nicodemism (chapter three), I place each of the five translations in its particular context, investigating prefaces, appendices, marginalia, and translation methods to discover how and why individuals used Quatre sermons (chapters four to six). Like Calvin in 1552, those who brought Quatre sermons to English readers were not primarily concerned with Nicodemism. Rather, the malleability of Calvin’s Nicodemite as polemical opponent and the flexibility of Quatre sermons as a sequence of discrete, interrelated parts made it popular with those eager to press Calvin into the service of a variety of diverse goals he could not have imagined, including turning his anti-Nicodemism against fellow members of the English church.