Where do amino acids get attached to tRNA and where is it synthesized?

Question

Some very basic parts of transcription/translation seem to be left out in various literature. I can't find the answer to this anywhere:

How exactly is tRNA synthesized? I realize that mRNA is synthesized through transcription and I know a lot about that. However tRNA is supposedly synthesized the same way but every time you read about transcription they just talk about how the mRNA then gets this and that...?

Where do the amino acids get attached? Is it in the nucleus or outside the nucleus?

Thanks.

Answer 1

A pre-tRNA is transcribed from tRNA genes in DNA by RNA polymerase III. Processing occurs in the nucleus, where a 5' sequence is cleaved by RNase P, the 3's CCA motif is added, and ~10% of the nucleotides are substituted. The tRNA are transported out via the pore complexes. Aminoacyl-tRNA synthetase enzymes attach amino acids in the cytoplasm in a 2-step reaction that requires ATP. You'll find there's a unique splicing mechanism in tRNA that additionally splices out an anticodon intron which is abesnt in mature tRNA's:

The wikipedia article notes RNA Pol III generally recognizes internal control elements rather than upstream control elements as in a normal gene.

Source: Qiagen

Source: Molecular Cell Biology. 4th edition.

Addendum: I said in my post that tRNA is charged in the cytoplasm, this is somewhat true. In mammalian cells, we also see that tRNA are charged in the nucleus as well, and it might aid in the export of some of these charged tRNAs. (Source)