scholarly journals Faculty Opinions recommendation of A cytosine methyltransferase homologue is essential for repeat-induced point mutation in Neurospora crassa.

2002 ◽  
Author(s):  
David Catcheside
Keyword(s):  
Neurospora Crassa ◽  
Point Mutation ◽  
Cytosine Methyltransferase ◽  
Repeat Induced Point Mutation

scholarly journals Regulation of DIM-2-dependent repeat-induced point mutation (RIP) by the recombination-independent homologous DNA pairing in Neurospora crassa

2021 ◽  
Author(s):  
Florian Carlier ◽  
Tinh-Suong Nguyen ◽  
Alexey K. Mazur ◽  
Eugene Gladyshev
Keyword(s):  
Neurospora Crassa ◽  
Point Mutation ◽  
Base Pairs ◽  
Substrate Preferences ◽  
Relative Contribution ◽  
Repeat Units ◽  
Sequence Recognition ◽  
Cytosine Methyltransferase ◽  
Flanking Regions ◽  
Repeat Induced Point Mutation

ABSTRACTRepeat-induced point mutation (RIP) is a genetic process that creates cytosine-to-thymine (C-to-T) transitions in duplicated genomic sequences in fungi. RIP detects duplications irrespective of their origin, particular sequence, coding capacity, or genomic positions. Previous studies suggested that RIP involves a cardinally new mechanism of sequence recognition that operates on intact double-stranded DNAs. In the fungus Neurospora crassa, RIP can be mediated by a putative C5-cytosine methyltransferase (CMT) RID or/and a canonical CMT DIM-2. These distinct RIP pathways feature opposite substrate preferences: RID-dependent RIP is largely limited to the duplicated sequences, whereas DIM-2-dependent RIP preferentially mutates adjacent non-repetitive regions. Using DIM-2-dependent RIP as a principal readout of repeat recognition, here we show that GC-rich repeats promote stronger RIP compared to AT-rich repeats (independently of their intrinsic propensities to become mutated), with the relative contribution of AT base-pairs being close to zero. We also show that direct repeats promote much more efficient DIM-2-dependent RIP than inverted repeats; both the spacer DNA between the repeat units (the linker) and the flanking regions are similarly affected by this process. These and other results support the idea that repeat recognition for RIP involves formation of many short interspersed quadruplexes between homologous double-stranded DNAs, which need to undergo concomitant changes in their linking number to accommodate pairing.SUMMARYDuring repeat-induced point mutation (RIP) gene-sized duplications of genomic DNA are detected by a mechanism that likely involves direct pairing of homologous double-stranded DNAs. We show that DIM-2-dependent RIP, triggered by closely-positioned duplications, is strongly affected by their relative orientations (direct versus inverted). We also show that GC-rich repeats promote RIP more effectively than AT-rich repeats. These results support a model in which homologous dsDNAs can pair by establishing interspersed quadruplex-based contacts with concomitant changes in their supercoiling status.

scholarly journals Synthesis of Signals for De Novo DNA Methylation in Neurospora crassa

2003 ◽  
Vol 23 (7) ◽  
pp. 2379-2394 ◽  
Author(s):  
Hisashi Tamaru ◽  
Eric U. Selker
Keyword(s):  
Dna Methylation ◽  
Neurospora Crassa ◽  
Point Mutation ◽  
Dna Sequences ◽  
De Novo ◽  
Test Site ◽  
Minor Groove ◽  
Binding Motif ◽  
Repeat Induced Point Mutation

ABSTRACT Most 5-methylcytosine in Neurospora crassa occurs in A:T-rich sequences high in TpA dinucleotides, hallmarks of repeat-induced point mutation. To investigate how such sequences induce methylation, we developed a sensitive in vivo system. Tests of various 25- to 100-bp synthetic DNA sequences revealed that both T and A residues were required on a given strand to induce appreciable methylation. Segments composed of (TAAA) n or (TTAA) n were the most potent signals; 25-mers induced robust methylation at the special test site, and a 75-mer induced methylation elsewhere. G:C base pairs inhibited methylation, and cytosines 5′ of ApT dinucleotides were particularly inhibitory. Weak signals could be strengthened by extending their lengths. A:T tracts as short as two were found to cooperate to induce methylation. Distamycin, which, like the AT-hook DNA binding motif found in proteins such as mammalian HMG-I, binds to the minor groove of A:T-rich sequences, suppressed DNA methylation and gene silencing. We also found a correlation between the strength of methylation signals and their binding to an AT-hook protein (HMG-I) and to activities in a Neurospora extract. We propose that de novo DNA methylation in Neurospora cells is triggered by cooperative recognition of the minor groove of multiple short A:T tracts. Similarities between sequences subjected to repeat-induced point mutation in Neurospora crassa and A:T-rich repeated sequences in heterochromatin in other organisms suggest that related mechanisms control silent chromatin in fungi, plants, and animals.

RIP (repeat induced point mutation) as a tool in the analysis of P-450 and sterol biosynthesis in Neurospora crassa

1991 ◽  
Vol 19 (3) ◽  
pp. 799-802 ◽  
Author(s):  
Ian F. Connerton ◽  
Shelly M. Deane ◽  
Jenny A. Butters ◽  
R. S. Thomas Loeffler ◽  
Derek W. Hollomon
Keyword(s):  
Neurospora Crassa ◽  
Point Mutation ◽  
Sterol Biosynthesis ◽  
Repeat Induced Point Mutation

scholarly journals The Neurospora crassa standard Oak Ridge background exhibits an atypically efficient meiotic silencing by unpaired DNA

2018 ◽  
Author(s):  
Dev Ashish Giri ◽  
Ajith V. Pankajam ◽  
Koodali T. Nishant ◽  
Durgadas P. Kasbekar
Keyword(s):  
Genetic Variation ◽  
Neurospora Crassa ◽  
Point Mutation ◽  
Genetic Background ◽  
Meiotic Silencing ◽  
Genetic Studies ◽  
Oak Ridge ◽  
General Abstract ◽  
Repeat Induced Point Mutation ◽  
Made In

AbstractMeiotic silencing by unpaired DNA (MSUD) was discovered in crosses made in the standard Oak Ridge (OR) genetic background of Neurospora crassa. However, MSUD often was decidedly less efficient when the OR-derived MSUD tester strains were crossed with wild-isolated strains (W), which suggested either that sequence heterozygosity in tester x W crosses suppresses MSUD, or that OR represents the MSUD-conducive extreme in the range of genetic variation in MSUD efficiency. Our results support the latter model. MSUD was much less efficient in near-isogenic crosses made in a novel N. crassa B/S1 and the N. tetrasperma 85 genetic backgrounds. Possibly, regulatory cues that in other genetic backgrounds calibrate the MSUD response are missing from OR. The OR versus B/S1 difference appears to be determined by loci on chromosomes 1, 2, and 5. OR crosses heterozygous for a duplicated chromosome segment (Dp) have for long been known to exhibit an MSUD-dependent barren phenotype. However, inefficient MSUD in N. tetrasperma 85 made Dp-heterozygous crosses non-barren. This is germane to our earlier demonstration that Dps can act as dominant suppressors of repeat-induced point mutation (RIP). Occasionally, during ascospore partitioning rare asci contained >8 nuclei, and round ascospores dispersed less efficiently than spindle-shaped ones.General abstractIn crosses made in the standard OR genetic background of Neurospora crassa, an RNAi-mediated process called MSUD efficiently silences any gene not properly paired with its homologue during meiosis. We found that MSUD was not as efficient in comparable crosses made in the N. crassa B/S1 and N. tetrasperma 85 backgrounds, suggesting that efficient MSUD is not necessarily the norm in Neurospora. Indeed, using OR strains for genetic studies probably fortuitously facilitated the discovery of MSUD and its suppressors. As few as three unlinked loci appear to underlie the OR versus B/S1 difference in MSUD.

Sign in / Sign up

Export Citation Format

Share Document