Proteins that regulate transcription often also play an architectural role in the genome. Thus, it has been difficult to define with precision the distinctions between transcription factors and nucleoid-associated proteins (NAPs). Anachronistic descriptions of NAPs as 'histone-like' implied an organizational function in a bacterial chromatin-like complex. Definitions based on protein abundance, regulatory mechanisms, target gene number, or the features of their DNA-binding sites are insufficient as marks of distinction, and trying to distinguish transcription factors and NAPs based on their ranking within regulatory hierarchies or positions in gene-control networks is also unsatisfactory. The terms 'transcription factor' and 'NAP' are ad hoc operational definitions with each protein lying along a spectrum of structural and functional features extending from highly specific actors with few gene targets to those with a pervasive influence on the transcriptome. The Streptomyces BldC protein is used to illustrate these issues.

中文翻译：

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转录因子何时是NAP？

调节转录的蛋白质通常在基因组中也起建筑作用。因此，很难精确地定义转录因子和核苷相关蛋白（NAP）之间的区别。NAP的过时描述为“组蛋白样”，暗示了细菌染色质样复合物中的组织功能。基于蛋白质丰度，调控机制，靶基因数目或其DNA结合位点特征的定义不足以作为区分的标记，并试图根据它们在调控层次结构或基因控制中的位置来区分转录因子和NAP网络也不尽人意。术语“转录因子”和“ NAP” 是特定的操作定义，每种蛋白质都具有一系列结构和功能特征，从高度特异性的，几乎没有基因靶标的参与者延伸到对转录组有普遍影响的参与者。链霉菌BldC蛋白用于说明这些问题。