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Transcription of DNA and further splicing of mRNA is regulated by various transcription factors, small nuclear RNAs and so on; similarly such related mechanisms as transposition of transposons.

All such factors and mechanisms, including those linked to inter-cellular signalling mediated by peptides and various so-called epigenetic enzymatic processes, require and are dependent upon transcription itself, in the first place of DNA codons.

What mechanism then is supposed ultimately to control the expression, eventually as peptides translated from mRNA, of information encoded in DNA; if it is not peptides thus encoded? That is, since transcription depends on transcription factors which themselves require transcription requiring further transcription factors, does this mean that in the entirety of its function, DNA controls itself?

How then can DNA and its transcription be conceived as a such a self-controlling function?

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Transcription of DNA is ultimately controlled by "various transcription factors, small nuclear RNAs and so on" in the cell.

The molecules which make up the "various transcription factors", etc. are already present in the cell when a new transcription begins. As you note, most all of these molecules are themselves dependent on the transcription of DNA, but also of the availability of component molecules (e.g. nucleotides, amino acids) and of processing mechanisms such as ribosomes.

So, a new instance of transcription requires a working cellular environment, and that environment was created and maintained as directed by DNA molecules at an earlier time. Usually those DNA molecules were exactly the same as the ones from which the transcription is proceeding. Occasionally, those DNA molecules would have been physically different, but adequately compatible, such as the source chromosomes which were copied during mitosis to create the current DNA molecule.

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