Cells impose optimal noise control mechanism in diverse situations to cope with distinct environmental cues. Sometimes, it is desirable for the cell to utilize fluctuations for noise-driven processes. In other cases, noise can be harmful to the cell to show optimal fitness. It is, therefore, important to unravel the noise propagation mechanism inside the cell. Such noise controlling mechanism is accomplished by using gene transcription regulatory networks. One such gene regulatory network is feed-forward loop, having three regulatory nodes S, X and Y. Here, we consider the most abundant type 1 of coherent and incoherent feed-forward loops with both OR and AND logic functions, forming four different architectures. In OR logic function, the functions representing S and X act additively for the regulation of Y, while in AND logic function, the same functions (S and X) act multiplicatively for the regulation of Y. Measurement of susceptibility of the signal at output Y is done using elasticity of each regulation in FFLs. Using susceptibility, we demonstrate the nature of pathway integration by which one-step and two-step pathways get overlapped. The integration type is competitive for motifs having OR gate, while it is noncompetitive for the same with AND gate. The pathway integration property explains the output noise behavior of the motifs properly but cannot infer about the mechanism by which the upstream noise propagates to output. To account this, the total output noise is decomposed, which results in integrated noise as an additional noise source along with pathway-specific noise components. The integrated noise is found to appear as a consequence of integration between the pathways and has different functional characteristics explaining noise amplification and noise attenuation property of coherent and incoherent feed-forward loops, respectively. The noise decomposition also quantifies the contribution of different noise sources toward total noise. Finally, the noise propagation is being tuned as a function of input signal noise and its time scale of fluctuations, which shows considerable intrinsic noise strength and relatively slow relaxation time scale causes a higher degree of noise propagation in FFLs.

细胞在不同情况下施加最佳噪声控制机制以应对不同的环境线索。有时，单元希望将波动用于噪声驱动的过程。在其他情况下，噪音可能会损害细胞以显示最佳适应度。因此，解开细胞内部的噪声传播机制非常重要。这种噪声控制机制是通过使用基因转录调控网络来实现的。一种这样的基因调控网络是前馈回路，具有三个调控节点S、X和Y. 在这里，我们考虑具有 OR 和 AND 逻辑功能的最丰富的第 1 类相干和非相干前馈循环，形成四种不同的架构。在 OR 逻辑函数中，代表S和X的函数对Y的调节作用相加，而在 AND 逻辑函数中，相同的函数（S和X）对Y的调节作用相乘。在输出Y处测量信号的敏感性是使用 FFL 中每个法规的弹性完成的。使用敏感性，我们证明了一步和两步路径重叠的途径整合的性质。集成类型对于具有 OR 门的motifs 具有竞争性，而对于具有 AND 门的motifs 则是非竞争性的。路径整合属性正确解释了模体的输出噪声行为，但无法推断上游噪声传播到输出的机制。为了解决这个问题，总输出噪声被分解，这导致集成噪声作为附加噪声源以及特定于路径的噪声分量。发现集成噪声是路径之间集成的结果，并且具有不同的功能特性，分别解释了相干和非相干前馈环路的噪声放大和噪声衰减特性。噪声分解还量化了不同噪声源对总噪声的贡献。最后，噪声传播被调整为输入信号噪声及其波动时间尺度的函数，这显示出相当大的固有噪声强度和相对缓慢的弛豫时间尺度导致 FFL 中更高程度的噪声传播。