bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protein Variation in ADH and ADH-RELATED in Drosophila pseudoobscura: Linkage Disequilibrium Between Single Nucleotide Polymorphisms and Protein Alleles
Authors: Schaeffer Stephen W , Walthour C Scott , Toleno Donna M , Olek Anna T , Miller Ellen L 
Published: April 2021

Abstract
A 3.5-kb segment of the alcohol dehydrogenase (Adh) region that includes the Adh and Adh-related genes was sequenced in 139 Drosophila pseudoobscura strains collected from 13 populations. The Adh gene encodes four protein alleles and rejects a neutral model of protein evolution with the McDonald-Kreitman test, although the number of segregating synonymous sites is too high to conclude that adaptive selection has operated. The Adh-related gene encodes 18 protein haplotypes and fails to reject an equilibrium neutral model. The populations fail to show significant geographic differentiation of the Adh-related haplotypes. Eight of 404 single nucleotide polymorphisms (SNPs) in the Adh region were in significant linkage disequilibrium with three ADHR protein alleles. Coalescent simulations with and without recombination were used to derive the expected levels of significant linkage disequilibrium between SNPs and 18 protein haplotypes. Maximum levels of linkage disequilibrium are expected for protein alleles at moderate frequencies. In coalescent models without recombination, linkage disequilibrium decays between SNPs and high frequency haplotypes because common alleles mutate to haplotypes that are rare or that reach moderate frequency. The implication of this study is that linkage disequilibrium mapping has the highest probability of success with disease-causing alleles at frequencies of 10%.
Dynamics of Microsatellite Divergence Under Stepwise Mutation and Proportional Slippage/Point Mutation Models
Authors: Calabrese Peter P , Durrett Richard T , Aquadro Charles F 
Published: April 2021

Abstract
Recently Kruglyak, Durrett, Schug, and Aquadro showed that microsatellite equilibrium distributions can result from a balance between polymerase slippage and point mutations. Here, we introduce an elaboration of their model that keeps track of all parts of a perfect repeat and a simplification that ignores point mutations. We develop a detailed mathematical theory for these models that exhibits properties of microsatellite distributions, such as positive skewness of allele lengths, that are consistent with data but are inconsistent with the predictions of the stepwise mutation model. We use our theoretical results to analyze the successes and failures of the genetic distances (δμ)2 and DSW when used to date four divergences: African vs. non-African human populations, humans vs. chimpanzees, Drosophila melanogaster vs. D. simulans, and sheep vs. cattle. The influence of point mutations explains some of the problems with the last two examples, as does the fact that these genetic distances have large stochastic variance. However, we find that these two features are not enough to explain the problems of dating the human-chimpanzee split. One possible explanation of this phenomenon is that long microsatellites have a mutational bias that favors contractions over expansions.
Codon Usage Bias Covaries With Expression Breadth and the Rate of Synonymous Evolution in Humans, but This Is Not Evidence for Selection
Authors: Urrutia Araxi O , Hurst Laurence D 
Published: April 2021

Abstract
In numerous species, from bacteria to Drosophila, evidence suggests that selection acts even on synonymous codon usage: codon bias is greater in more abundantly expressed genes, the rate of synonymous evolution is lower in genes with greater codon bias, and there is consistency between genes in the same species in which codons are preferred. In contrast, in mammals, while nonequal use of alternative codons is observed, the bias is attributed to the background variance in nucleotide concentrations, reflected in the similar nucleotide composition of flanking noncoding and exonic third sites. However, a systematic examination of the covariants of codon usage controlling for background nucleotide content has yet to be performed. Here we present a new method to measure codon bias that corrects for background nucleotide content and apply this to 2396 human genes. Nearly all (99%) exhibit a higher amount of codon bias than expected by chance. The patterns associated with selectively driven codon bias are weakly recovered: Broadly expressed genes have a higher level of bias than do tissue-specific genes, the bias is higher for genes with lower rates of synonymous substitutions, and certain codons are repeatedly preferred. However, while these patterns are suggestive, the first two patterns appear to be methodological artifacts. The last pattern reflects in part biases in usage of nucleotide pairs. We conclude that we find no evidence for selection on codon usage in humans.
A Filamentous Growth Response Mediated by the Yeast Mating Pathway
Authors: Erdman Scott , Snyder Michael 
Published: April 2021

Abstract
Haploid cells of the budding yeast Saccharomyces cerevisiae respond to mating pheromones by arresting their cell-division cycle in G1 and differentiating into a cell type capable of locating and fusing with mating partners. Yeast cells undergo chemotactic cell surface growth when pheromones are present above a threshold level for morphogenesis; however, the morphogenetic responses of cells to levels of pheromone below this threshold have not been systematically explored. Here we show that MATa haploid cells exposed to low levels of the α-factor mating pheromone undergo a novel cellular response: cells modulate their division patterns and cell shape, forming colonies composed of filamentous chains of cells. Time-lapse analysis of filament formation shows that its dynamics are distinct from that of pseudohyphal growth; during pheromone-induced filament formation, daughter cells are delayed relative to mother cells with respect to the timing of bud emergence. Filament formation requires the RSR1(BUD1), BUD8, SLK1/BCK1, and SPA2 genes and many elements of the STE11/STE7 MAP kinase pathway; this response is also independent of FAR1, a gene involved in orienting cell polarization during the mating response. We suggest that mating yeast cells undergo a complex response to low levels of pheromone that may enhance the ability of cells to search for mating partners through the modification of cell shape and alteration of cell-division patterns.
Dual Mutations Reveal Interactions Between Components of Oxidative Phosphorylation in Kluyveromyces lactis
Authors: Clark-Walker G D , Chen X J 
Published: April 2021

Abstract
Loss of mtDNA or mitochondrial protein synthesis cannot be tolerated by wild-type Kluyveromyces lactis. The mitochondrial function responsible for ρ0-lethality has been identified by disruption of nuclear genes encoding electron transport and F0-ATP synthase components of oxidative phosphorylation. Sporulation of diploid strains heterozygous for disruptions in genes for the two components of oxidative phosphorylation results in the formation of nonviable spores inferred to contain both disruptions. Lethality of spores is thought to result from absence of a transmembrane potential, ΔΨ, across the mitochondrial inner membrane due to lack of proton pumping by the electron transport chain or reversal of F1F0-ATP synthase. Synergistic lethality, caused by disruption of nuclear genes, or ρ0-lethality can be suppressed by the atp2.1 mutation in the β-subunit of F1-ATPase. Suppression is viewed as occurring by an increased hydrolysis of ATP by mutant F1, allowing sufficient electrogenic exchange by the translocase of ADP in the matrix for ATP in the cytosol to maintain ΔΨ. In addition, lethality of haploid strains with a disruption of AAC encoding the ADP/ATP translocase can be suppressed by atp2.1. In this case suppression is considered to occur by mutant F1 acting in the forward direction to partially uncouple ATP production, thereby stimulating respiration and relieving detrimental hyperpolarization of the inner membrane. Participation of the ADP/ATP translocase in suppression of ρ0-lethality is supported by the observation that disruption of AAC abolishes suppressor activity of atp2.1.
Overlapping Functions of the Saccharomyces cerevisiae Mre11, Exo1 and Rad27 Nucleases in DNA Metabolism
Authors: Moreau Sylvie , Morgan Elizabeth A , Symington Lorraine S 
Published: April 2021

Abstract
MRE11 functions in several aspects of DNA metabolism, including meiotic recombination, double-strand break repair, and telomere maintenance. Although the purified protein exhibits 3′ to 5′ exonuclease and endonuclease activities in vitro, Mre11 is implicated in the 5′ to 3′ resection of duplex ends in vivo. The mre11-H125N mutation, which eliminates the nuclease activities of Mre11, causes an accumulation of unprocessed double-strand breaks (DSBs) in meiosis, but no defect in processing HO-induced DSBs in mitotic cells, suggesting the existence of redundant activities. Mutation of EXO1, which encodes a 5′ to 3′ exonuclease, was found to increase the ionizing radiation sensitivity of both mre11Δ and mre11-H125N strains, but the exo1 mre11-H125N strain showed normal kinetics of mating-type switching and was more radiation resistant than the mre11Δ strain. This suggests that other nucleases can compensate for loss of the Exo1 and Mre11 nucleases, but not of the Mre11-Rad50-Xrs2 complex. Deletion of RAD27, which encodes a flap endonuclease, causes inviability in mre11 strains. When mre11-H125N was combined with the leaky rad27-6, the double mutants were viable and no more γ-ray sensitive than the mre11-H125N strain. This suggests that the double mutant defect is unlikely to be due to defective DSB processing.
Interval Mapping of Quantitative Trait Loci in Autotetraploid Species
Authors: Hackett C A , Bradshaw J E , McNicol J W 
Published: April 2021

AbstractThis article presents a method for QTL interval mapping in autotetraploid species for a full-sib family derived by crossing two parents. For each offspring, the marker information on each chromosome is used to identify possible configurations of chromosomes inherited from the two parents and the locations of crossovers on these chromosomes. A branch and bound algorithm is used to identify configurations with the minimum number of crossovers. From these configurations, the conditional probability of each possible QTL genotype for a series of positions along the chromosome can be estimated. An iterative weighted regression is then used to relate the trait values to the QTL genotype probabilities. A simulation study is performed to assess this approach and to investigate the effects of the proportion of codominant to dominant markers, the heritability, and the population size. We conclude that the method successfully locates QTL and estimates their parameters accurately, and we discuss different modes of action of the QTL that may be modeled.
Meiotic Alterations in CAG Repeat Tracts
Authors: Schweitzer Jill Kuglin , Reinke Shanda S , Livingston Dennis M 
Published: April 2021

Abstract
We have investigated meiotic changes in CAG repeat tracts embedded in a yeast chromosome. Repeat tracts undergo either conversion events between homologs or expansion and contraction events that appear to be confined to a single chromatid. We did not find evidence for conversion of tract interruptions or excess exchange of flanking markers.
Light and Clock Expression of the Neurospora Clock Gene frequency Is Differentially Driven by but Dependent on WHITE COLLAR-2
Authors: Collett Michael A , Garceau Norm , Dunlap Jay C , Loros Jennifer J 
Published: April 2021

Abstract
Visible light is thought to reset the Neurospora circadian clock by acting through heterodimers of the WHITE COLLAR-1 and WHITE COLLAR-2 proteins to induce transcription of the frequency gene. To characterize this photic entrainment we examined frq expression in constant light, under which condition the mRNA and protein of this clock gene were strongly induced. In continuous illumination FRQ accumulated in a highly phosphorylated state similar to that seen at subjective dusk, the time at which a step from constant light to darkness sets the clock. Examination of frq expression in several wc-2 mutant alleles surprisingly revealed differential regulation when frq expression was compared between constant light, following a light pulse, and darkness (clock-driven expression). Construction of a wc-2 null strain then demonstrated that WC-2 is absolutely required for both light and clock-driven frq expression, in contrast to previous expectations based on presumptive nulls containing altered Zn-finger function. Additionally, we found that frq light signal transduction differs from that of other light-regulated genes. Thus clock and light-driven frq expression is differentially regulated by, but dependent on, WC-2.
Cloning and Characterization of the Tribolium castaneum Eye-Color Genes Encoding Tryptophan Oxygenase and Kynurenine 3-Monooxygenase
Authors: Lorenzen Marcé D , Brown Susan J , Denell Robin E , Beeman Richard W 
Published: April 2021

Abstract
The use of eye-color mutants and their corresponding genes as scorable marker systems has facilitated the development of transformation technology in Drosophila and other insects. In the red flour beetle, Tribolium castaneum, the only currently available system for germline transformation employs the exogenous marker gene, EGFP, driven by an eye-specific promoter. To exploit the advantages offered by eye-pigmentation markers, we decided to develop a transformant selection system for Tribolium on the basis of mutant rescue. The Tribolium orthologs of the Drosophila eye-color genes vermilion (tryptophan oxygenase) and cinnabar (kynurenine 3-monooxygenase) were cloned and characterized. Conceptual translations of Tc vermilion (Tcv) and Tc cinnabar (Tccn) are 71 and 51% identical to their respective Drosophila orthologs. We used RNA interference (RNAi) to show that T. castaneum larvae lacking functional Tcv or Tccn gene products also lack the pigmented eyespots observed in wild-type larvae. Five available eye-color mutations were tested for linkage to Tcv or Tccn via recombinational mapping. No linkage was found between candidate mutations and Tccn. However, tight linkage was found between Tcv and the white-eye mutation white, here renamed vermilionwhite (vw). Molecular analysis indicates that 80% of the Tcv coding region is deleted in vw beetles. These observations suggest that the Tribolium eye is pigmented only by ommochromes, not pteridines, and indicate that Tcv is potentially useful as a germline transformation marker.
Novel Non-Mendelian Determinant Involved in the Control of Translation Accuracy in Saccharomyces cerevisiae
Authors: Volkov Kirill V , Aksenova Anna Yu , Soom Malle J , Osipov Kirill V , Svitin Anton V , Kurischko Cornelia , Shkundina Irina S , Ter-Avanesyan Michael D , Inge-Vechtomov Sergey G , Mironova Ludmila N 
Published: April 2021

Abstract
Two cytoplasmically inherited determinants related by their manifestation to the control of translation accuracy were previously described in yeast. Cells carrying one of them, [PSI+], display a nonsense suppressor phenotype and contain a prion form of the Sup35 protein. Another element, [PIN+], determines the probability of de novo generation of [PSI+] and results from a prion form of several proteins, which can be functionally unrelated to Sup35p. Here we describe a novel nonchromosomal determinant related to the SUP35 gene. This determinant, designated [ISP+], was identified as an antisuppressor of certain sup35 mutations. We observed its loss upon growth on guanidine hydrochloride and subsequent spontaneous reappearance with high frequency. The reversible curability of [ISP+] resembles the behavior of yeast prions. However, in contrast to known prions, [ISP+] does not depend on the chaperone protein Hsp104. Though manifestation of both [ISP+] and [PSI+] is related to the SUP35 gene, the maintenance of [ISP+] does not depend on the prionogenic N-terminal domain of Sup35p and Sup35p is not aggregated in [ISP+] cells, thus ruling out the possibility that [ISP+] is a specific form of [PSI+]. We hypothesize that [ISP+] is a novel prion involved in the control of translation accuracy in yeast.
Saccharomyces cerevisiae MPT5 and SSD1 Function in Parallel Pathways to Promote Cell Wall Integrity
Authors: Kaeberlein Matt , Guarente Leonard 
Published: April 2021

Abstract
Yeast MPT5 (UTH4) is a limiting component for longevity. We show here that MPT5 also functions to promote cell wall integrity. Loss of Mpt5p results in phenotypes associated with a weakened cell wall, including sorbitol-remedial temperature sensitivity and sensitivities to calcofluor white and sodium dodecyl sulfate. Additionally, we find that mutation of MPT5, in the absence of SSD1-V, is lethal in combination with loss of either Ccr4p or Swi4p. These synthetic lethal interactions are suppressed by the SSD1-V allele. Furthermore, we have provided evidence that the short life span caused by loss of Mpt5p is due to a weakened cell wall. This cell wall defect may be the result of abnormal chitin biosynthesis or accumulation. These analyses have defined three genetic pathways that function in parallel to promote cell integrity: an Mpt5p-containing pathway, an Ssd1p-containing pathway, and a Pkc1p-dependent pathway. This work also provides evidence that post-transcriptional regulation is likely to be important both for maintaining cell integrity and for promoting longevity.
Genetic Interactions of Yeast Eukaryotic Translation Initiation Factor 5A (eIF5A) Reveal Connections to Poly(A)-Binding Protein and Protein Kinase C Signaling
Authors: Valentini Sandro R , Casolari Jason M , Oliveira Carla C , Silver Pamela A , McBride Anne E 
Published: April 2021

Abstract
The highly conserved eukaryotic translation initiation factor eIF5A has been proposed to have various roles in the cell, from translation to mRNA decay to nuclear protein export. To further our understanding of this essential protein, three temperature-sensitive alleles of the yeast TIF51A gene have been characterized. Two mutant eIF5A proteins contain mutations in a proline residue at the junction between the two eIF5A domains and the third, strongest allele encodes a protein with a single mutation in each domain, both of which are required for the growth defect. The stronger tif51A alleles cause defects in degradation of short-lived mRNAs, supporting a role for this protein in mRNA decay. A multicopy suppressor screen revealed six genes, the overexpression of which allows growth of a tif51A-1 strain at high temperature; these genes include PAB1, PKC1, and PKC1 regulators WSC1, WSC2, and WSC3. Further results suggest that eIF5A may also be involved in ribosomal synthesis and the WSC/PKC1 signaling pathway for cell wall integrity or related processes.
The Cytoplasmic End of Transmembrane Domain 3 Regulates the Activity of the Saccharomyces cerevisiae G-Protein-Coupled α-Factor Receptor
Authors: Parrish William , Eilers Markus , Ying Weiwen , Konopka James B 
Published: April 2021

Abstract
The binding of α-factor to its receptor (Ste2p) activates a G-protein-signaling pathway leading to conjugation of MATa cells of the budding yeast S. cerevisiae. We conducted a genetic screen to identify constitutively activating mutations in the N-terminal region of the α-factor receptor that includes transmembrane domains 1–5. This approach identified 12 unique constitutively activating mutations, the strongest of which affected polar residues at the cytoplasmic ends of transmembrane domains 2 and 3 (Asn84 and Gln149, respectively) that are conserved in the α-factor receptors of divergent yeast species. Targeted mutagenesis, in combination with molecular modeling studies, suggested that Gln149 is oriented toward the core of the transmembrane helix bundle where it may be involved in mediating an interaction with Asn84. These residues appear to play specific roles in maintaining the inactive conformation of the protein since a variety of mutations at either position cause constitutive receptor signaling. Interestingly, the activity of many mammalian G-protein-coupled receptors is also regulated by conserved polar residues (the E/DRY motif) at the cytoplasmic end of transmembrane domain 3. Altogether, the results of this study suggest a conserved role for the cytoplasmic end of transmembrane domain 3 in regulating the activity of divergent G-protein-coupled receptors.
Cytogenetic Analysis of the Third Chromosome Heterochromatin of Drosophila melanogaster
Authors: Koryakov Dmitry E , Zhimulev Igor F , Dimitri Patrizio 
Published: April 2021

Abstract
Previous cytological analysis of heterochromatic rearrangements has yielded significant insight into the location and genetic organization of genes mapping to the heterochromatin of chromosomes X, Y, and 2 of Drosophila melanogaster. These studies have greatly facilitated our understanding of the genetic organization of heterochromatic genes. In contrast, the 12 essential genes known to exist within the mitotic heterochromatin of chromosome 3 have remained only imprecisely mapped. As a further step toward establishing a complete map of the heterochomatic genetic functions in Drosophila, we have characterized several rearrangements of chromosome 3 by using banding techniques at the level of mitotic chromosome. Most of the rearrangement breakpoints were located in the dull fluorescent regions h49, h51, and h58, suggesting that these regions correspond to heterochromatic hotspots for rearrangements. We were able to construct a detailed cytogenetic map of chromosome 3 heterochromatin that includes all of the known vital genes. At least 7 genes of the left arm (from l(3)80Fd to l(3)80Fj) map to segment h49–h51, while the most distal genes (from l(3)80Fa to l(3)80Fc) lie within the h47–h49 portion. The two right arm essential genes, l(3)81Fa and l(3)81Fb, are both located within the distal h58 segment. Intriguingly, a major part of chromosome 3 heterochromatin was found to be “empty,” in that it did not contain either known genes or known satellite DNAs.
Comparative Analysis of the Human Dystrophin and Utrophin Gene Structures
Authors: Pozzoli Uberto , Sironi Manuela , Cagliani Rachele , Comi Giacomo P , Bardoni Alessandra , Bresolin Nereo 
Published: April 2021

Abstract
We present analysis of intronic sequences in the human DMD and UTRN genes. In both genes accumulation of repeated elements could account for intron expansion. Out-of-frame rod-domain exons have stronger splice sites and are separated by significantly longer introns as compared to in-frame exons. These features are unique for the two homologs and not shared by other spectrin superfamily genes.
Multiple Subunits of the Caenorhabditis elegans Anaphase-Promoting Complex Are Required for Chromosome Segregation During Meiosis I
Authors: Davis Edward S , Wille Lucia , Chestnut Barry A , Sadler Penny L , Shakes Diane C , Golden Andy 
Published: April 2021

Abstract
Two genes, originally identified in genetic screens for Caenorhabditis elegans mutants that arrest in metaphase of meiosis I, prove to encode subunits of the anaphase-promoting complex or cyclosome (APC/C). RNA interference studies reveal that these and other APC/C subunits are essential for the segregation of chromosomal homologs during meiosis I. Further, chromosome segregation during meiosis I requires APC/C functions in addition to the release of sister chromatid cohesion.