transkriptide

Transkriptide, in molecular biology, are RNA molecules synthesized from a DNA template during transcription. They serve as intermediates between the genome and the functional products of gene expression. Transcripts are produced by RNA polymerases, with RNA polymerase II generating most protein-coding messenger RNAs in eukaryotes, as well as many noncoding RNAs, while bacteria rely on a single RNA polymerase.

The main classes of transcripts include messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA), together with regulatory or noncoding RNAs such as microRNA (miRNA), small interfering RNA (siRNA), and small nucleolar RNA (snoRNA). In bacteria, transcripts are often polycistronic, encoding multiple proteins, whereas in eukaryotes transcripts are typically monocistronic and subject to extensive processing.

Transcription begins at promoter regions, aided by transcription factors in eukaryotes. Initiation is followed by elongation, during which the RNA strand is synthesized complementary to the DNA template. Termination signals end transcription, with mechanisms varying among organisms. In eukaryotes, transcripts often undergo RNA processing before becoming mature RNA: 5’ capping, intron splicing, and 3’ polyadenylation for mRNA, as well as specialized processing for rRNA and tRNA. Alternative splicing can generate multiple protein isoforms from a single gene.

Regulation of transcription involves promoter elements, enhancers, silencers, transcription factors, and epigenetic marks such as DNA methylation and histone modifications. Transcript abundance is studied in transcriptomics using methods like RNA sequencing, microarrays, and quantitative PCR.

Transcripts are central to gene expression and cellular function; dysregulation of transcription is associated with numerous diseases, including cancer and developmental disorders.