Project description:We calculated global RNA half lives for all genes in the cyanobacteria Synechococcus sp. strain PCC 7002. Samples from three replicates of the WT strain were taken before and following the addition of the antibiotic rifampicin to stop nascent transcription. RNA spike-ins were added for normalization and using the number of RNA-sequencing reads we were able to calculate half lives for genes, transcripts, and for each position on the genome.
Project description:Dinoflagellates possess many physiological processes that appear to be under post-transcriptional control. However, the extent to which their genes are regulated post-transcriptionally remains unresolved. To gain insight into the role of differential mRNA stability in dinoflagellates, we biosynthetically labeled RNA with 4-thiouracil to isolate newly transcribed and pre-existing RNA pools in Karenia brevis. These isolated fractions were then used for analysis of global mRNA stability by hybridization to a K. brevis microarray. Global K. brevis mRNA half-lives were calculated from the ratio of newly transcribed/pre-existing RNA for 7086 array features using the online software HALO (Half-life Organizer). Overall, mRNA half-lives were substantially longer than reported in other organisms studied at the global level, ranging from 42 minutes to greater than 3 days, with a median of 33 hours. Thirteen percent of messages showed a half-life of 3 days, demonstrating their stability throughtout the course of the cell cycle and divison. Consistent with well-documented trends observed in other organisms, housekeeping processes, including energy metabolism and transport, were significantly enriched in the most highly stable messages. Shorter-lived transcripts included a higher proportion of transcriptional regulation, stress response, and other response/regulatory processes.
Project description:We measured half-lives of 21,248 mRNA 3’ isoforms in yeast by rapidly depleting RNA polymerase II from the nucleus and performing direct RNA sequencing throughout the decay process. Interestingly, the half-lives of mRNA isoforms from the same gene, including nearly identical isoforms, often vary widely. Based on clusters of isoforms with different half-lives, we identify hundreds of sequences conferring stabilization or destabilization upon mRNAs terminating downstream. One class of stabilizing element is a polyU sequence that can interact with poly(A) tails, inhibit the association of poly(A) binding protein, and confer increased stability upon introduction into ectopic transcripts. More generally, destabilization and stabilization elements are linked to the degree to which the poly(A) tail can engage in double-stranded structures. Isoforms engineered to fold into 3’ stem-loop structures not involving the poly(A) tail exhibit even longer half-lives. We suggest that double-stranded structures at the 3’ ends are a major determinant of mRNA stability. Half-lives of 21,248 mRNA 3’ isoforms in yeast were measured by rapidly depleting RNA polymerase II from the nucleus and performing direct RNA sequencing throughout the decay process.
Project description:We measured half-lives of 21,248 mRNA 3’ isoforms in yeast by rapidly depleting RNA polymerase II from the nucleus and performing direct RNA sequencing throughout the decay process. Interestingly, the half-lives of mRNA isoforms from the same gene, including nearly identical isoforms, often vary widely. Based on clusters of isoforms with different half-lives, we identify hundreds of sequences conferring stabilization or destabilization upon mRNAs terminating downstream. One class of stabilizing element is a polyU sequence that can interact with poly(A) tails, inhibit the association of poly(A) binding protein, and confer increased stability upon introduction into ectopic transcripts. More generally, destabilization and stabilization elements are linked to the degree to which the poly(A) tail can engage in double-stranded structures. Isoforms engineered to fold into 3’ stem-loop structures not involving the poly(A) tail exhibit even longer half-lives. We suggest that double-stranded structures at the 3’ ends are a major determinant of mRNA stability.
Project description:We calculated half-life values of mRNAs quantified by RNA-Seq by a suitable method of normalization. We determined the half-lives of more than 2200 mRNAs in the Stenotrophomonas maltophilia D457 wild-type strain and in an isogenic RNase G deficient mutant. Median half-lives were 2,74 and 3 min in the wild-type and the rng-deficient mutant respectively. We found an overall enhancement of half-life times of mRNAs when the gene encoding RNase G is lacking, showing that many RNAs are targets of RNase G in S. maltophilia. For achieving such goal, we propose a method for the normalization of RNA-Seq based studies on global bacterial mRNA decay.
Project description:Dinoflagellates possess many physiological processes that appear to be under post-transcriptional control. However, the extent to which their genes are regulated post-transcriptionally remains unresolved. To gain insight into the role of differential mRNA stability in dinoflagellates, we biosynthetically labeled RNA with 4-thiouracil to isolate newly transcribed and pre-existing RNA pools in Karenia brevis. These isolated fractions were then used for analysis of global mRNA stability by hybridization to a K. brevis microarray. Global K. brevis mRNA half-lives were calculated from the ratio of newly transcribed/pre-existing RNA for 7086 array features using the online software HALO (Half-life Organizer). Overall, mRNA half-lives were substantially longer than reported in other organisms studied at the global level, ranging from 42 minutes to greater than 3 days, with a median of 33 hours. Thirteen percent of messages showed a half-life of 3 days, demonstrating their stability throughtout the course of the cell cycle and divison. Consistent with well-documented trends observed in other organisms, housekeeping processes, including energy metabolism and transport, were significantly enriched in the most highly stable messages. Shorter-lived transcripts included a higher proportion of transcriptional regulation, stress response, and other response/regulatory processes. Log phase cultures (n=6) were exposed to 0.2 mM 4-thiouracil for 2h to biosynthetically label newly transcribed RNA and total RNA was extracted. Following extraction, RNA was biotinylated to allow for purification of the thiolated newly synthesized RNA from the total RNA pool using streptavidin coated magnetic beads. From each replicate 3 pools of RNA, total RNA, pre-exisiting RNA, and newly synthesized RNA, were Cy3 labeled and hybridized to microarrys in a one color format. Based on the appearance of bioanlayzer profiles, total and pre-existing RNA were treated as total RNA, while newly synthesized RNA was treated as mRNA in the labeling protocol.
Project description:Nonsense-mediated mRNA decay (NMD) pathway promotes the degradation of several mRNA species, including transcripts containing a premature termination codon. Here,we measured global mRNA half-lives in NMD deficient and wild-type (WT) embryonic stem cells (ESCs). This allowed us to discriminate which transcripts are affected by NMD. Several transcripts had an impaired half-life in Smg5 and Smg6 KO ESCs compared to WT. They belong to different pathways and cellular processing indicating that NMD regulates multiple processes in the cells. Finally, majority of the transcripts had an impairment on the half-life in both Smg5 and Smg6 KO ESCs indicating that endo- and exonucleolityc branches of the NMD pathway target the same mRNAs.
Project description:This work aimed at analysing mRNA half lives in drug resistant and in drug sensitive strains of C. albicans (Gu4 and Gu5 azole susceptible and resistant clinical isolates (franz et al., 1999)), using the transcriptional inhibitor thiolutine.
Project description:We estimated global mRNA half-lives by blocking transcription and measuring mRNA levels at different times after transcriptional shut-off.