The Coupling of Alternative Splicing and Nonsense-Mediated mRNA Decay

Most human genes exhibit alternative splicing, but not all alternatively spliced transcripts produce functional proteins. Computational and experimental results indicate that a substantial fraction of alternative splicing events in humans result in mRNA isoforms that harbor a premature termination codon (PTC). These transcripts are predicted to be degraded by the nonsense-mediated mRNA decay (NMD) pathway. One explanation for the abundance of PTC-containing isoforms is that they represent splicing errors that are identified and degraded by the NMD pathway. Another potential explanation for this startling observation is that cells may link alternative splicing and NMD to regulate the abundance of mRNA transcripts. This mechanism, which we call "Regulated Unproductive Splicing and Translation" (RUST), has been experimentally shown to regulate expression of a wide variety of genes in many organisms from yeast to human. It is frequently employed for autoregulation of proteins that affect the splicing process itself. Thus, alternative splicing and NMD act together to play an important role in regulating gene expression

Carrier Phase Synchronization Techniques at Very Low SNR for Deep Space Missions

International audienceDeep space communication systems operate on very long distance and the on-board energy generator capacity is very limited which results in a very low signal to noise ratio (SNR) at the reception. This is the reason why near Shannon limit error correcting codes such as Turbo codes and LDPC are used. Nevertheless, to take advantage of the coding gain, the coherent demodulation is mandatory and the carrier phase synchronization must be performed at a more restrictive SNR. To optimize the transmission spectral efficiency, The CCSDS has recommended the GMSK modulation for deep space missions. This paper discusses with a carrier phase recovery scheme derived from maximum a posteriori (MAP) criterion and Laurent expansion for GMSK BTb = 0.5 modulation scheme. One of the key technologies to improve the SNR at the ground station, while reducing the infrastructure installation cost and offering more flexibility, is the use of receiving-antenna array instead of a single large aperture antenna. We propose in this paper a novel method for antenna arraying which enhances the combiner performance by several dB in terms of SNR