RESUMEN
The RPB1 mutants in the foot region of RNA polymerase II affect the assembly of the complex by altering the correct association of both the Rpb6 and the Rpb4/7 dimer. Assembly defects alter both transcriptional activity as well as the amount of enzyme associated with genes. Here, we show that the global transcriptional analysis of foot mutants reveals the activation of an environmental stress response (ESR), which occurs at a permissive temperature under optimal growth conditions. Our data indicate that the ESR that occurs in foot mutants depends mostly on a global post-transcriptional regulation mechanism which, in turn, depends on Rpb4-mRNA imprinting. Under optimal growth conditions, we propose that Rpb4 serves as a key to globally modulate mRNA stability as well as to coordinate transcription and decay. Overall, our results imply that post-transcriptional regulation plays a major role in controlling the ESR at both the transcription and mRNA decay levels.
Asunto(s)
ARN Polimerasa II/genética , Proteínas de Saccharomyces cerevisiae/genética , Estrés Fisiológico/genética , Transcripción Genética , Impresión Molecular , Mutación , Estabilidad del ARN/genética , ARN Mensajero/genética , Saccharomyces cerevisiaeRESUMEN
Recent papers have provided insight into the cytoplasmic assembly of RNA polymerase II (RNA pol II) and its transport to the nucleus. However, little is known about the mechanisms governing its nuclear assembly, stability, degradation, and recycling. We demonstrate that the foot of RNA pol II is crucial for the assembly and stability of the complex, by ensuring the correct association of Rpb1 with Rpb6 and of the dimer Rpb4-Rpb7 (Rpb4/7). Mutations at the foot affect the assembly and stability of the enzyme, a defect that is offset by RPB6 overexpression, in coordination with Rpb1 degradation by an Asr1-independent mechanism. Correct assembly is a prerequisite for the proper maintenance of several transcription steps. In fact, assembly defects alter transcriptional activity and the amount of enzyme associated with the genes, affect C-terminal domain (CTD) phosphorylation, interfere with the mRNA-capping machinery, and possibly increase the amount of stalled RNA pol II. In addition, our data show that TATA-binding protein (TBP) occupancy does not correlate with RNA pol II occupancy or transcriptional activity, suggesting a functional relationship between assembly, Mediator, and preinitiation complex (PIC) stability. Finally, our data help clarify the mechanisms governing the assembly and stability of RNA pol II.
Asunto(s)
ARN Polimerasa II/química , ARN Polimerasa II/metabolismo , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , ARN Polimerasas Dirigidas por ADN/química , ARN Polimerasas Dirigidas por ADN/genética , ARN Polimerasas Dirigidas por ADN/metabolismo , Estabilidad de Enzimas/genética , Genes Fúngicos , Complejo Mediador/metabolismo , Modelos Biológicos , Mutación , Estructura Terciaria de Proteína , Subunidades de Proteína , Caperuzas de ARN/metabolismo , ARN Polimerasa II/genética , ARN de Hongos/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteína de Unión a TATA-Box/metabolismo , Transcripción GenéticaRESUMEN
Stapedial reflex is used, amongst other pathologies, for the study of otosclerosis. In this retrospective study we have collected 188 cases of patients with otosclerosis whose diagnosis has been confirmed surgically and their first line relatives. We have performed a descriptive analysis of audiometric tests, tympanometries and ipsilateral stapedial reflexes in relation with the evolutive phase of the disease. Transmission hypoacusis has been seen in 54%, mixed hypoacusis in 29% and sensorineural hypoacusis 8% of cases. On and OFF stapedial reflexes have been seen in 18%, inverted reflexes in 46% and absent reflexes in 27% of cases. The original drawings of the different types of reflexes during the evolution of otosclerosis can be seen in the four figures shown in the study: normal reflexes; ON and OFF a, b and c types; inverted a and b; and absent reflexes. The clinical evolutive phase and the audiometric and impedance tests have been correlated. Through Chi-square (p < 0.001), we have obtained a statistical significance in relation to the use of stapedial reflexes. Also it has been suggested the use of provoked stapedial reflexes in patients with sub clinical otosclerosis in order to diagnose the disease. We conclude that the knowledge of the evolutive morphology os stapedial reflexes in otosclerosis helps diagnostic capacity.